Pub Date : 1991-01-30DOI: 10.1109/MEMSYS.1991.114786
K. Noguchi, H. Fujita, M. Suzuki, N. Yoshimura
The coefficient of maximum static friction was measured and evaluated for various thin films deposited by plasma CVD (chemical vapor deposition), the sol-gel method, and vacuum evaporation on a glass substrate and a silicon wafer. Millimeter-size movers driven electrostatically slide on these films to measure friction coefficients. From the experimental results, it was found that the friction coefficients are dependent on the type of specimen and the preparation method. When the glass plate was used as the mover's bottom, the coefficients of maximum static friction for a ZrO/sub 2/ (sol-gel) film, an Al (evaporation) film, a Si (evaporation) film, a glass substrate, a silicon wafer, and a SiN/sub x/ (CVD) were found to be small. Against the silicon wafer, an SiO/sub 2/ (evaporation) film, a glass substrate, and a ZrO/sub 2/ (sol-gel) film give small coefficients of maximum static friction.<>
{"title":"The measurements of friction on micromechatronics elements","authors":"K. Noguchi, H. Fujita, M. Suzuki, N. Yoshimura","doi":"10.1109/MEMSYS.1991.114786","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114786","url":null,"abstract":"The coefficient of maximum static friction was measured and evaluated for various thin films deposited by plasma CVD (chemical vapor deposition), the sol-gel method, and vacuum evaporation on a glass substrate and a silicon wafer. Millimeter-size movers driven electrostatically slide on these films to measure friction coefficients. From the experimental results, it was found that the friction coefficients are dependent on the type of specimen and the preparation method. When the glass plate was used as the mover's bottom, the coefficients of maximum static friction for a ZrO/sub 2/ (sol-gel) film, an Al (evaporation) film, a Si (evaporation) film, a glass substrate, a silicon wafer, and a SiN/sub x/ (CVD) were found to be small. Against the silicon wafer, an SiO/sub 2/ (evaporation) film, a glass substrate, and a ZrO/sub 2/ (sol-gel) film give small coefficients of maximum static friction.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126756960","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114795
H. Ozdemir, J.C. Smith
An energy band diagram model has been utilized to characterize the electrochemical behavior of Si. A new passivation phenomenon is presented and the underlying mechanisms of this new passivation effect are analyzed with the aid of the energy band diagram representation of the Si/KOH interface. The new effect consists in the fact that, in the presence of a pn-junction at the Si/KOH interface, the p-type substrate does not etch even when it is under open circuit conditions, although one would normally expect that both sides of the junction would be etched away. An explanation of this new passivation effect is based on an inversion layer formation at the p-type surface. It is concluded that a detailed understanding of the etching/passivation mechanisms outlined enables processes to be designed with selective etching of any desired layer, particularly including low resistivities. This, in turn, makes possible the simultaneous production of optimized active devices in retained layers. An example of what can be achieved with the electrochemical passivation technique is shown consisting of a passivated n-type bridge over a cavity etched from a p-type substrate.<>
{"title":"Band model for explaining new effects observed in electromechanical micromachining of Si","authors":"H. Ozdemir, J.C. Smith","doi":"10.1109/MEMSYS.1991.114795","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114795","url":null,"abstract":"An energy band diagram model has been utilized to characterize the electrochemical behavior of Si. A new passivation phenomenon is presented and the underlying mechanisms of this new passivation effect are analyzed with the aid of the energy band diagram representation of the Si/KOH interface. The new effect consists in the fact that, in the presence of a pn-junction at the Si/KOH interface, the p-type substrate does not etch even when it is under open circuit conditions, although one would normally expect that both sides of the junction would be etched away. An explanation of this new passivation effect is based on an inversion layer formation at the p-type surface. It is concluded that a detailed understanding of the etching/passivation mechanisms outlined enables processes to be designed with selective etching of any desired layer, particularly including low resistivities. This, in turn, makes possible the simultaneous production of optimized active devices in retained layers. An example of what can be achieved with the electrochemical passivation technique is shown consisting of a passivated n-type bridge over a cavity etched from a p-type substrate.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129369522","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114790
P. Dario, R. Valleggi, M. Pardini, A. Sabatini
The design and fabrication of a miniature catheter-tip structure incorporating shape memory alloy actuators are described. The ability of the active catheter-tip to generate large displacement and force at low frequency has been evaluated in an experimental set-up intended to replicate, in vitro, conditions similar to those encountered within a body cavity. The experimental results indicate that the proposed structure works properly, and that it could be improved in order to obtain a device truly usable for intracavitary operations.<>
{"title":"A miniature device for medical intracavitary intervention","authors":"P. Dario, R. Valleggi, M. Pardini, A. Sabatini","doi":"10.1109/MEMSYS.1991.114790","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114790","url":null,"abstract":"The design and fabrication of a miniature catheter-tip structure incorporating shape memory alloy actuators are described. The ability of the active catheter-tip to generate large displacement and force at low frequency has been evaluated in an experimental set-up intended to replicate, in vitro, conditions similar to those encountered within a body cavity. The experimental results indicate that the proposed structure works properly, and that it could be improved in order to obtain a device truly usable for intracavitary operations.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134086310","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114761
S. Egawa, T. Niino, T. Higuchi
The authors present a variety of surface-drive film actuators and discuss their characteristics. An actuator consisting of a stator with three-phase 420 mu m-pitched electrodes and a slightly conductive slider was developed previously. A finer 100 mu m-pitched stator was fabricated and operated. A two-phase stator, whose fabrication is easier, was developed, and a two-phase 50 mu m-pitched stator was fabricated and tested. The need for conductivity on the slider narrows the application field of the actuator. An ion-charged motor which can drive most thin insulating films and uses an air ionizer to give charges on the slider was developed. The produced motive force is numerically and experimentally analyzed. The optimal gap between the electrodes and the slider surface is found to be around 20% of electrode pitch. The 100 mu m-pitched stator drives a slider at +or-250 V, 1000 Hz, producing 20 N/m/sup 2/ at maximum. Comparison between developed actuators demonstrates the advantages of fabricating fine electrodes.<>
{"title":"Film actuators: Planar, electrostatic surface-drive actuators","authors":"S. Egawa, T. Niino, T. Higuchi","doi":"10.1109/MEMSYS.1991.114761","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114761","url":null,"abstract":"The authors present a variety of surface-drive film actuators and discuss their characteristics. An actuator consisting of a stator with three-phase 420 mu m-pitched electrodes and a slightly conductive slider was developed previously. A finer 100 mu m-pitched stator was fabricated and operated. A two-phase stator, whose fabrication is easier, was developed, and a two-phase 50 mu m-pitched stator was fabricated and tested. The need for conductivity on the slider narrows the application field of the actuator. An ion-charged motor which can drive most thin insulating films and uses an air ionizer to give charges on the slider was developed. The produced motive force is numerically and experimentally analyzed. The optimal gap between the electrodes and the slider surface is found to be around 20% of electrode pitch. The 100 mu m-pitched stator drives a slider at +or-250 V, 1000 Hz, producing 20 N/m/sup 2/ at maximum. Comparison between developed actuators demonstrates the advantages of fabricating fine electrodes.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"130 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126803237","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114800
J. Branebjerg, C. Eijkel, J. Gardeniers, F.C.M. van de Pol
The authors report on the use of the HF anodic etching technique to realize monocrystalline silicon microstructures. As it has been established that the rate of the silicon etching reactions is mainly governed by the availability of holes at the silicon surface which is in contact with the etching solution, the definition of the geometry of microstructures can be accomplished by methods which affect the hole concentration locally. It is demonstrated that the methods which exploit the sharp selectivity of HF anodic etching between p-Si and n-Si show good potential and can be used to manufacture suspended beams, making use of masked implantation of phosphorus for geometry definition. It is concluded that this technology offers new opportunities in the field of micromachining of silicon for micromechanical applications.<>
{"title":"Dopant selective HF anodic etching of silicon-for the realization of low-doped monocrystalline silicon microstructures","authors":"J. Branebjerg, C. Eijkel, J. Gardeniers, F.C.M. van de Pol","doi":"10.1109/MEMSYS.1991.114800","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114800","url":null,"abstract":"The authors report on the use of the HF anodic etching technique to realize monocrystalline silicon microstructures. As it has been established that the rate of the silicon etching reactions is mainly governed by the availability of holes at the silicon surface which is in contact with the etching solution, the definition of the geometry of microstructures can be accomplished by methods which affect the hole concentration locally. It is demonstrated that the methods which exploit the sharp selectivity of HF anodic etching between p-Si and n-Si show good potential and can be used to manufacture suspended beams, making use of masked implantation of phosphorus for geometry definition. It is concluded that this technology offers new opportunities in the field of micromachining of silicon for micromechanical applications.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132741553","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114780
W. Tjhen, T. Tamagawa, C. Ye, C. Hsueh, P. Schiller, D. Polla
Zinc oxide and ferroelectrics of the lead zirconate titanate (PZT) family are candidates for piezoelectric actuation as well as sensing elements in microelectromechanical systems. In this work the relevant properties of the thin film forms of these materials are characterized, including the induced stress, the Young's modulus, and the electromechanical coupling (piezoelectric) constants. Pyroelectric and dielectric properties (permittivity and resistivity) were also investigated. The mechanical properties in thin film ZnO and PZT were found to be favorable for their use in micromachining. The piezoelectric coefficients found for these films are also favorable for microactuation. Electrical properties in both ZnO and PZT were found to be sensitive to substrate material stress surface and surface condition. The relatively high pyroelectric coefficients measured in these films suggest the possible need for ambient temperature-cancellation schemes in micromechanical structures. Demonstration of micromachining using these films suggests that the film deposition technology as it exists now is suitable for achieving piezoelectrically induced motion on the microscale.<>
{"title":"Properties of piezoelectric thin films for micromechanical devices and systems","authors":"W. Tjhen, T. Tamagawa, C. Ye, C. Hsueh, P. Schiller, D. Polla","doi":"10.1109/MEMSYS.1991.114780","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114780","url":null,"abstract":"Zinc oxide and ferroelectrics of the lead zirconate titanate (PZT) family are candidates for piezoelectric actuation as well as sensing elements in microelectromechanical systems. In this work the relevant properties of the thin film forms of these materials are characterized, including the induced stress, the Young's modulus, and the electromechanical coupling (piezoelectric) constants. Pyroelectric and dielectric properties (permittivity and resistivity) were also investigated. The mechanical properties in thin film ZnO and PZT were found to be favorable for their use in micromachining. The piezoelectric coefficients found for these films are also favorable for microactuation. Electrical properties in both ZnO and PZT were found to be sensitive to substrate material stress surface and surface condition. The relatively high pyroelectric coefficients measured in these films suggest the possible need for ambient temperature-cancellation schemes in micromechanical structures. Demonstration of micromachining using these films suggests that the film deposition technology as it exists now is suitable for achieving piezoelectrically induced motion on the microscale.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132989211","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114782
K. Ikuta, S. Makita, S. Arimoto
A unique transmission mechanism using a non-contact magnetic gear (NCMG) is proposed for micro and miniature electromechanical systems. A miniature NCMG has been produced and the basic characteristics were evaluated experimentally. The theoretical approach for analyzing the transmittable torque of the NCMG was developed and verified experimentally. It is concluded that the NCMG system has great potential for use in safe miniature transmission mechanisms for medical applications and in micro transmission systems for microelectromechanical systems.<>
{"title":"Non-contact magnetic gear for micro transmission mechanism","authors":"K. Ikuta, S. Makita, S. Arimoto","doi":"10.1109/MEMSYS.1991.114782","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114782","url":null,"abstract":"A unique transmission mechanism using a non-contact magnetic gear (NCMG) is proposed for micro and miniature electromechanical systems. A miniature NCMG has been produced and the basic characteristics were evaluated experimentally. The theoretical approach for analyzing the transmittable torque of the NCMG was developed and verified experimentally. It is concluded that the NCMG system has great potential for use in safe miniature transmission mechanisms for medical applications and in micro transmission systems for microelectromechanical systems.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123704222","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114781
K. Yanagisawa, A. Tago, T. Ohkubo, H. Kuwano
The characteristics of three types of magnetic microactuators made by silicon-based microfabrication are described. The microfabrication, actuator configuration, and dynamic characteristics of a fabricated microactuator with a planar coil are examined. This microactuator is shown to operate in the nanometer range. It has a conical soft-magnetic tip 10 microns high with a one-turn copper coil. This actuator will be applied to microvalves, micropumps, and microsyringes.<>
{"title":"Magnetic micro-actuator","authors":"K. Yanagisawa, A. Tago, T. Ohkubo, H. Kuwano","doi":"10.1109/MEMSYS.1991.114781","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114781","url":null,"abstract":"The characteristics of three types of magnetic microactuators made by silicon-based microfabrication are described. The microfabrication, actuator configuration, and dynamic characteristics of a fabricated microactuator with a planar coil are examined. This microactuator is shown to operate in the nanometer range. It has a conical soft-magnetic tip 10 microns high with a one-turn copper coil. This actuator will be applied to microvalves, micropumps, and microsyringes.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124865733","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114788
T. Lammerink, M. Elwenspoek, J. Fluitman
The authors present theoretical and experimental studies on optothermal excitation of bending-mode micromechanical resonators. The theory results in a prediction of induced bending moment (modulus and phase) as a function of the excitation frequency, the geometry of the structure, and material properties. It is shown that decisive roles are played by the absorption length of the material mu , the penetration depth of a thermal wave delta , and the thickness of the resonator. delta is a function of the excitation frequency while the resonance frequency depends on h. The theory results in design rules for optothermal resonators. It is shown that absorbing layers improve the efficiency of the optothermal transduction only in the case of transparent materials. Experiments agree well with theory.<>
{"title":"Optical excitation of micro-mechanical resonators","authors":"T. Lammerink, M. Elwenspoek, J. Fluitman","doi":"10.1109/MEMSYS.1991.114788","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114788","url":null,"abstract":"The authors present theoretical and experimental studies on optothermal excitation of bending-mode micromechanical resonators. The theory results in a prediction of induced bending moment (modulus and phase) as a function of the excitation frequency, the geometry of the structure, and material properties. It is shown that decisive roles are played by the absorption length of the material mu , the penetration depth of a thermal wave delta , and the thickness of the resonator. delta is a function of the excitation frequency while the resonance frequency depends on h. The theory results in design rules for optothermal resonators. It is shown that absorbing layers improve the efficiency of the optothermal transduction only in the case of transparent materials. Experiments agree well with theory.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121648333","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 : 1991-01-30DOI: 10.1109/MEMSYS.1991.114770
G. Fedder, R. Howe
Thermal microassembly techniques are demonstrated which extend the capabilities of surface micromachining technology. Bridges are cleanly severed by application of a single 30 mA, 100 mu s pulse. Delicately suspended microstructures are supported by tee bridges during wet etching of phosphosilicate glass, in order to reduce yield loss due to breakage and stiction to the substrate during rinsing and drying. The supports are subsequently severed to release the structure. Mechanical contacts are welded together with 30 mA of current, with a microprobe used to force together the contacts. Qualitative destructive tests indicate that the welded contact is robust. Electrostatic force applied by interdigitated electrodes is insufficient to initiate welding of polysilicon, possibly because the native oxide film must be penetrated to allow current to pass through the contact. Current vs. voltage measurements of polysilicon microbridges agree well with a first-order model, in which heat conduction and convection in air are neglected. Values of the voltage needed to melt the bridge are found to vary with bridge dimensions, because the bridge anchors are not perfect heat sinks.<>
{"title":"Thermal assembly of polysilicon microstructures","authors":"G. Fedder, R. Howe","doi":"10.1109/MEMSYS.1991.114770","DOIUrl":"https://doi.org/10.1109/MEMSYS.1991.114770","url":null,"abstract":"Thermal microassembly techniques are demonstrated which extend the capabilities of surface micromachining technology. Bridges are cleanly severed by application of a single 30 mA, 100 mu s pulse. Delicately suspended microstructures are supported by tee bridges during wet etching of phosphosilicate glass, in order to reduce yield loss due to breakage and stiction to the substrate during rinsing and drying. The supports are subsequently severed to release the structure. Mechanical contacts are welded together with 30 mA of current, with a microprobe used to force together the contacts. Qualitative destructive tests indicate that the welded contact is robust. Electrostatic force applied by interdigitated electrodes is insufficient to initiate welding of polysilicon, possibly because the native oxide film must be penetrated to allow current to pass through the contact. Current vs. voltage measurements of polysilicon microbridges agree well with a first-order model, in which heat conduction and convection in air are neglected. Values of the voltage needed to melt the bridge are found to vary with bridge dimensions, because the bridge anchors are not perfect heat sinks.<<ETX>>","PeriodicalId":258054,"journal":{"name":"[1991] Proceedings. IEEE Micro Electro Mechanical Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1991-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130080772","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：