Pub Date : 1994-09-12DOI: 10.1109/IROS.1994.407472
Shigang Li, M. Chiba, S. Tsuji
A human being often looks around to locate him/herself from the arrangement of surrounding objects. Here, the authors propose an idea to determine camera motion by line correspondence in omni-directional images. An omni-directional image has a 360 degree view and contains much more information than those taken by a conventional imaging method. Since the camera motion is estimated from line displacements in images and the line displacements change due to line arrangement in space and camera motion, an omni-directional view makes it possible to select a better line combination for estimating more accurate motion. Experimental results show that camera motion can be estimated more accurately using lines surrounding the camera in omni-directional images than using lines in a narrow view. First, the authors use lines surrounding the camera to determine the camera rotational component and find the true solution from multiple ones by voting from multiple line combinations. Then, the authors select an optimal line combination to estimate the translation component by examining their linear independence. Simulation and real-world experimental results are given.<>
{"title":"Estimating camera motion precisely from omni-directional images","authors":"Shigang Li, M. Chiba, S. Tsuji","doi":"10.1109/IROS.1994.407472","DOIUrl":"https://doi.org/10.1109/IROS.1994.407472","url":null,"abstract":"A human being often looks around to locate him/herself from the arrangement of surrounding objects. Here, the authors propose an idea to determine camera motion by line correspondence in omni-directional images. An omni-directional image has a 360 degree view and contains much more information than those taken by a conventional imaging method. Since the camera motion is estimated from line displacements in images and the line displacements change due to line arrangement in space and camera motion, an omni-directional view makes it possible to select a better line combination for estimating more accurate motion. Experimental results show that camera motion can be estimated more accurately using lines surrounding the camera in omni-directional images than using lines in a narrow view. First, the authors use lines surrounding the camera to determine the camera rotational component and find the true solution from multiple ones by voting from multiple line combinations. Then, the authors select an optimal line combination to estimate the translation component by examining their linear independence. Simulation and real-world experimental results are given.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"105 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121105312","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 : 1994-09-12DOI: 10.1109/IROS.1994.407504
N. Chong, Donghoon Choi, I. Suh
A hierarchical planning strategy for dextrous manipulation of multifingered hands with soft finger contact model is proposed. Dextrous manipulation planning can be divided into a high-level stage which specifies the position/orientation trajectories of the finger-tips on the object and a low-level stage which determines the contact forces and joint trajectories for the fingers. In the low-level stage, various nonlinear optimization problems are formulated according to the contact modes and integrated into a manipulation planning algorithm to find contact forces and joint velocities at each time step. Montana's contact equations (1988) are used for the high-level planning. A real-time compensation tactics to eliminate the trajectory errors of the object resulted from various uncertainties are also developed. Simulation results are presented and illustrated by employing a three-fingered hand manipulating a sphere to demonstrate the validity of the proposed strategy.<>
{"title":"Planning and error compensation for finite manipulation of soft-fingered hands","authors":"N. Chong, Donghoon Choi, I. Suh","doi":"10.1109/IROS.1994.407504","DOIUrl":"https://doi.org/10.1109/IROS.1994.407504","url":null,"abstract":"A hierarchical planning strategy for dextrous manipulation of multifingered hands with soft finger contact model is proposed. Dextrous manipulation planning can be divided into a high-level stage which specifies the position/orientation trajectories of the finger-tips on the object and a low-level stage which determines the contact forces and joint trajectories for the fingers. In the low-level stage, various nonlinear optimization problems are formulated according to the contact modes and integrated into a manipulation planning algorithm to find contact forces and joint velocities at each time step. Montana's contact equations (1988) are used for the high-level planning. A real-time compensation tactics to eliminate the trajectory errors of the object resulted from various uncertainties are also developed. Simulation results are presented and illustrated by employing a three-fingered hand manipulating a sphere to demonstrate the validity of the proposed strategy.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126160969","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 : 1994-09-12DOI: 10.1109/IROS.1994.407579
H. Sutanto, Rajeev Sharma
This paper describes two case studies of motion planning that uses a space called Perceptual Control Surface (PCS) introduced previously as a basis for visually controlling a robot manipulator. The motion planning problems discussed here are limited to dynamic robot hand positioning for interception tasks. Using this approach, a motion planning problem can be regarded as finding a path in robot's PCS which satisfies certain criteria. Qualitatively different tasks correspond to different type of paths in the PCS. These correspondences are discussed and techniques to find these different paths are outlined.<>
{"title":"Case studies of vision-based motion planning for robot interception tasks","authors":"H. Sutanto, Rajeev Sharma","doi":"10.1109/IROS.1994.407579","DOIUrl":"https://doi.org/10.1109/IROS.1994.407579","url":null,"abstract":"This paper describes two case studies of motion planning that uses a space called Perceptual Control Surface (PCS) introduced previously as a basis for visually controlling a robot manipulator. The motion planning problems discussed here are limited to dynamic robot hand positioning for interception tasks. Using this approach, a motion planning problem can be regarded as finding a path in robot's PCS which satisfies certain criteria. Qualitatively different tasks correspond to different type of paths in the PCS. These correspondences are discussed and techniques to find these different paths are outlined.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"284 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122966144","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 : 1994-09-12DOI: 10.1109/IROS.1994.407582
S. Rougeaux, N. Kita, Y. Kuniyoshi, S. Sakane, F. Chavand
This paper presents a stereo active vision system which performs tracking tasks on smoothly moving objects in complex backgrounds. Dynamic control of the vergence angle adapts the horopter geometry to the target position and allows to pick it up easily on the basis of stereoscopic disparity features. We introduce a novel vergence control strategy based on the computation of "virtual horopters" to track a target movement generating rapid changes of disparity. The control strategy is implemented on a binocular head, whose right and left pan angles are controlled independently. Experimental results of gaze holding on a smoothly moving target translating and rotating in a complex surrounding demonstrate the efficiency of the tracking system.<>
{"title":"Binocular tracking based on virtual horopters","authors":"S. Rougeaux, N. Kita, Y. Kuniyoshi, S. Sakane, F. Chavand","doi":"10.1109/IROS.1994.407582","DOIUrl":"https://doi.org/10.1109/IROS.1994.407582","url":null,"abstract":"This paper presents a stereo active vision system which performs tracking tasks on smoothly moving objects in complex backgrounds. Dynamic control of the vergence angle adapts the horopter geometry to the target position and allows to pick it up easily on the basis of stereoscopic disparity features. We introduce a novel vergence control strategy based on the computation of \"virtual horopters\" to track a target movement generating rapid changes of disparity. The control strategy is implemented on a binocular head, whose right and left pan angles are controlled independently. Experimental results of gaze holding on a smoothly moving target translating and rotating in a complex surrounding demonstrate the efficiency of the tracking system.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127576844","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 : 1994-09-12DOI: 10.1109/IROS.1994.407520
K. Kosuge, K. Takeo, T. Fukuda, Tunehiko Sugiura, Akira Sakai, Koji Yamada
This paper proposes an alternative control scheme for a teleoperation system which consists of a master arm, a slave arm and a virtual environment. For a given task, the operator manipulates a virtual environment and executes the task, a skill for the task is extracted through the manipulation, and the skill is transferred to the remote site to execute the task in real. First, the authors consider the design of a control algorithm for a master arm manipulating the virtual environment so that the system has a given dynamics for the operator and the environment. Then the authors consider the design of a control algorithm for the master-slave system manipulating the real environment so that the system has the same dynamics given to the manipulator of the virtual environment. By designing a control scheme, with which the master arm with a real environment and the master arm with a virtual environment have the same dynamics, the skill extracted from the operation of the virtual environment would be applied to the real task using the slave arm. The proposed control system is applied to an experimental master-slave manipulator and experimental results illustrate the effectiveness of the system.<>
{"title":"Unified approach for teleoperation of virtual and real environment for skill based teleoperation","authors":"K. Kosuge, K. Takeo, T. Fukuda, Tunehiko Sugiura, Akira Sakai, Koji Yamada","doi":"10.1109/IROS.1994.407520","DOIUrl":"https://doi.org/10.1109/IROS.1994.407520","url":null,"abstract":"This paper proposes an alternative control scheme for a teleoperation system which consists of a master arm, a slave arm and a virtual environment. For a given task, the operator manipulates a virtual environment and executes the task, a skill for the task is extracted through the manipulation, and the skill is transferred to the remote site to execute the task in real. First, the authors consider the design of a control algorithm for a master arm manipulating the virtual environment so that the system has a given dynamics for the operator and the environment. Then the authors consider the design of a control algorithm for the master-slave system manipulating the real environment so that the system has the same dynamics given to the manipulator of the virtual environment. By designing a control scheme, with which the master arm with a real environment and the master arm with a virtual environment have the same dynamics, the skill extracted from the operation of the virtual environment would be applied to the real task using the slave arm. The proposed control system is applied to an experimental master-slave manipulator and experimental results illustrate the effectiveness of the system.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131350029","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 : 1994-09-12DOI: 10.1109/IROS.1994.407459
Sukhan Lee, K. Jeong
A method for designing a robust time-delayed teleoperator control system based on H/sub /spl infin// optimization is presented. The proposed teleoperator control system deals with the robustness of teleoperation especially during the contact phase. In the approach phase where the slave end-effector is assumed to be in free space such that no significant modeling uncertainties are present, an optimal time-delayed teleoperator control system designed based on Smith's principle may suffice. However, in the contact phase where the uncertainties of contact time and environmental dynamics are of major concern, a time-delayed teleoperator control system should be designed to be robust to modeling uncertainties. Here, we apply the H/sub /spl infin// methodology for the design of such a robust time-delayed teleoperator control system. Simulation results show the validity of the proposed method.<>
{"title":"Design of robust time delayed teleoperator control system","authors":"Sukhan Lee, K. Jeong","doi":"10.1109/IROS.1994.407459","DOIUrl":"https://doi.org/10.1109/IROS.1994.407459","url":null,"abstract":"A method for designing a robust time-delayed teleoperator control system based on H/sub /spl infin// optimization is presented. The proposed teleoperator control system deals with the robustness of teleoperation especially during the contact phase. In the approach phase where the slave end-effector is assumed to be in free space such that no significant modeling uncertainties are present, an optimal time-delayed teleoperator control system designed based on Smith's principle may suffice. However, in the contact phase where the uncertainties of contact time and environmental dynamics are of major concern, a time-delayed teleoperator control system should be designed to be robust to modeling uncertainties. Here, we apply the H/sub /spl infin// methodology for the design of such a robust time-delayed teleoperator control system. Simulation results show the validity of the proposed method.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131601335","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 : 1994-09-12DOI: 10.1109/IROS.1994.407604
Yun-Su Ha, S. Yuta
Discusses the trajectory control for a wheeled inverse pendulum type mobile robot. The robot considered has two independent driving wheels on the same axle, and a gyro type sensor for measuring the inclination angular velocity of the body and rotary encoders to measure the wheels' rotation. The purpose of the authors' work is to make the robot autonomously navigate in a two dimensional plane while keeping balance of its body. The control algorithm consists of three parts; the balancing and velocity control, the heading control, and the trajectory control part. The authors designed and implemented a vehicle command system for this robot with the proposed algorithm. Experiments in real world navigation have been made by using the authors' experimental system "Yamabico Kurara".<>
{"title":"Trajectory tracking control for navigation of self-contained mobile inverse pendulum","authors":"Yun-Su Ha, S. Yuta","doi":"10.1109/IROS.1994.407604","DOIUrl":"https://doi.org/10.1109/IROS.1994.407604","url":null,"abstract":"Discusses the trajectory control for a wheeled inverse pendulum type mobile robot. The robot considered has two independent driving wheels on the same axle, and a gyro type sensor for measuring the inclination angular velocity of the body and rotary encoders to measure the wheels' rotation. The purpose of the authors' work is to make the robot autonomously navigate in a two dimensional plane while keeping balance of its body. The control algorithm consists of three parts; the balancing and velocity control, the heading control, and the trajectory control part. The authors designed and implemented a vehicle command system for this robot with the proposed algorithm. Experiments in real world navigation have been made by using the authors' experimental system \"Yamabico Kurara\".<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122671790","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 : 1994-09-12DOI: 10.1109/IROS.1994.407569
N. Miyake, M. Kametani, H. Sakairi
A new "dual control" robot control architecture is proposed. This control architecture endows a robot with human-like intelligent control capability similar to that of the human cerebrum. This improves robot adaptability to unpredictable circumstances, and allows a higher level of adaptability than conventional sensory feedback control, which depends on robot local sensory information, and which is limited to functions similar to those of the human cerebellum. With dual control, robot sensor data are processed qualitatively to recognize and understand global environmental situations, and decisions for real-time robot actions are then made. A closely coupled dual processor system with a dual bus system is proposed as the control architecture. The software system implemented for the hardware, as well as an example of the control, are also described.<>
{"title":"Hardware and software architecture for intelligent robot control-an approach to dual control architecture","authors":"N. Miyake, M. Kametani, H. Sakairi","doi":"10.1109/IROS.1994.407569","DOIUrl":"https://doi.org/10.1109/IROS.1994.407569","url":null,"abstract":"A new \"dual control\" robot control architecture is proposed. This control architecture endows a robot with human-like intelligent control capability similar to that of the human cerebrum. This improves robot adaptability to unpredictable circumstances, and allows a higher level of adaptability than conventional sensory feedback control, which depends on robot local sensory information, and which is limited to functions similar to those of the human cerebellum. With dual control, robot sensor data are processed qualitatively to recognize and understand global environmental situations, and decisions for real-time robot actions are then made. A closely coupled dual processor system with a dual bus system is proposed as the control architecture. The software system implemented for the hardware, as well as an example of the control, are also described.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121166905","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 : 1994-09-12DOI: 10.1109/IROS.1994.407506
D. Caldwell, R. K. Reddy
Hydraulic, pneumatic and electrical systems form the principle power sources that have been used to operate robots in industrial environments. However, when considering the needs of advanced robotics, one of the most fundamental requirements and problems is the provision of a suitable energy source to power the robot in a nonindustrial, often remote site. This work is aimed at designing a portable power supply that will operate efficiently and effectively in an untethered environment using a chemical fuel. Initially a feasibility study was undertaken to identify the different energy sources that are most widely used in the field of industrial robots, noting their relative advantages and disadvantages. Subsequently, the report focuses on the design, implementation and testing of an internal combustion based system that will be used to provide the drive source to a compressor which in turn will produce a constant air supply via a clutch and a series of gear mechanisms. Development and application of the mobile power supply is detailed. The silencing of the system is also analysed to reduce the noise level and allow operation in an enclosed/restricted environment as well as in the open atmosphere. This chemo-pneumatic power source is subsequently shown in operation driving pneumatic muscle actuators used in the construction of a high power/weight dexterous (3 finger 1 thumb) hand.<>
{"title":"A chemo-pneumatic drive source for flexible operation of pneumatic muscle actuators","authors":"D. Caldwell, R. K. Reddy","doi":"10.1109/IROS.1994.407506","DOIUrl":"https://doi.org/10.1109/IROS.1994.407506","url":null,"abstract":"Hydraulic, pneumatic and electrical systems form the principle power sources that have been used to operate robots in industrial environments. However, when considering the needs of advanced robotics, one of the most fundamental requirements and problems is the provision of a suitable energy source to power the robot in a nonindustrial, often remote site. This work is aimed at designing a portable power supply that will operate efficiently and effectively in an untethered environment using a chemical fuel. Initially a feasibility study was undertaken to identify the different energy sources that are most widely used in the field of industrial robots, noting their relative advantages and disadvantages. Subsequently, the report focuses on the design, implementation and testing of an internal combustion based system that will be used to provide the drive source to a compressor which in turn will produce a constant air supply via a clutch and a series of gear mechanisms. Development and application of the mobile power supply is detailed. The silencing of the system is also analysed to reduce the noise level and allow operation in an enclosed/restricted environment as well as in the open atmosphere. This chemo-pneumatic power source is subsequently shown in operation driving pneumatic muscle actuators used in the construction of a high power/weight dexterous (3 finger 1 thumb) hand.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121282394","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 : 1994-09-12DOI: 10.1109/IROS.1994.407523
R. Sturges, S. Laowattana
This paper addresses automatic assembly with passive rather than active compliant devices. Previous work has shown that in an ideal manufacturing environment three assembly primitives (prismatic insertions, threaded fits and general path insertions) exhibit a high level of difficulty. None of these are reliably assemblable under sensor-based force control or with an ordinary remote center compliance (RCC) device. In this paper, the authors extend the science of part mating and apply dexterity theory to synthesize a passive assembly device for precision fits of three-dimensional prismatic parts. This spatial remote center compliance (SRCC) obviates sensor-based and force control approaches to precision assembly of non-axisymmetric parts.<>
{"title":"Passive assembly of non-axisymmetric rigid parts","authors":"R. Sturges, S. Laowattana","doi":"10.1109/IROS.1994.407523","DOIUrl":"https://doi.org/10.1109/IROS.1994.407523","url":null,"abstract":"This paper addresses automatic assembly with passive rather than active compliant devices. Previous work has shown that in an ideal manufacturing environment three assembly primitives (prismatic insertions, threaded fits and general path insertions) exhibit a high level of difficulty. None of these are reliably assemblable under sensor-based force control or with an ordinary remote center compliance (RCC) device. In this paper, the authors extend the science of part mating and apply dexterity theory to synthesize a passive assembly device for precision fits of three-dimensional prismatic parts. This spatial remote center compliance (SRCC) obviates sensor-based and force control approaches to precision assembly of non-axisymmetric parts.<<ETX>>","PeriodicalId":437805,"journal":{"name":"Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128953537","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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