Pub Date : 2000-02-22DOI: 10.1109/NRSC.2000.838959
S. El-Khamy, E. Gelenbe, H. Abdelbaki
A neural network based direct sequence spread spectrum code synchronization system is proposed. The's system is based on training a recurrent random neural network (RNN) model on all the possible phases of the used spreading code. The trained network can then be used at the receiver for the initial coarse alignment of the local code phase and the received code. One advantage of this technique over the conventional synchronization techniques is that the phase of the received PN code can be decided without searching the potential code phases. Also the RNN, after being trained, can have a simple hardware realization that makes it candidate for implementation as a dedicated chip. This makes the neural network based technique faster and more robust than the conventional techniques. Computer simulations, carried out on maximal length sequences of length N=7 and N=15, show that the proposed system cast effectively indicate the phase of the received code even with very low signal to noise ratios.
{"title":"Neural network based spread spectrum PN code acquisition system","authors":"S. El-Khamy, E. Gelenbe, H. Abdelbaki","doi":"10.1109/NRSC.2000.838959","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838959","url":null,"abstract":"A neural network based direct sequence spread spectrum code synchronization system is proposed. The's system is based on training a recurrent random neural network (RNN) model on all the possible phases of the used spreading code. The trained network can then be used at the receiver for the initial coarse alignment of the local code phase and the received code. One advantage of this technique over the conventional synchronization techniques is that the phase of the received PN code can be decided without searching the potential code phases. Also the RNN, after being trained, can have a simple hardware realization that makes it candidate for implementation as a dedicated chip. This makes the neural network based technique faster and more robust than the conventional techniques. Computer simulations, carried out on maximal length sequences of length N=7 and N=15, show that the proposed system cast effectively indicate the phase of the received code even with very low signal to noise ratios.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122836112","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838904
S. El-Khamy, A. El-Marakby
Shaping the array factor of an adaptive antenna array to obtain interference suppression is a difficult task due to the computational complexity, slow convergence rates and the high cost requirements. Although some antenna synthesis techniques can be used to reduce the side-lobe levels (and hence reduce the effect of interference arriving outside the main lobe), the resulting array factors suffer from the increased width of the main lobe. This degradation is more profound in phased arrays operating at large scanning angles and hence, the performance will be limited in many applications requiring radiation patterns with narrow steerable main lobes. In this paper, a technique based on radial-basis function neural networks (RBFNN) is presented for shaping the array factor of phased linear arrays to have relatively low side-lobe levels without affecting the beamwidth requirements of the main lobe. Both uniform and nonuniform linear arrays with initially low sidelobe levels, such as Tschebyscheff arrays are considered. The simulation results show that the use of RBFNN minimizes the sidelobe levels while keeping a predetermined width of main lobes. Thus, highly improved patterns with very deep sidelobe and increased directivity, with beam steering capabilities, are obtained.
{"title":"Using radial-basis function neural networks to shape the array factor and reduce the side-lobe levels of phased antenna arrays","authors":"S. El-Khamy, A. El-Marakby","doi":"10.1109/NRSC.2000.838904","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838904","url":null,"abstract":"Shaping the array factor of an adaptive antenna array to obtain interference suppression is a difficult task due to the computational complexity, slow convergence rates and the high cost requirements. Although some antenna synthesis techniques can be used to reduce the side-lobe levels (and hence reduce the effect of interference arriving outside the main lobe), the resulting array factors suffer from the increased width of the main lobe. This degradation is more profound in phased arrays operating at large scanning angles and hence, the performance will be limited in many applications requiring radiation patterns with narrow steerable main lobes. In this paper, a technique based on radial-basis function neural networks (RBFNN) is presented for shaping the array factor of phased linear arrays to have relatively low side-lobe levels without affecting the beamwidth requirements of the main lobe. Both uniform and nonuniform linear arrays with initially low sidelobe levels, such as Tschebyscheff arrays are considered. The simulation results show that the use of RBFNN minimizes the sidelobe levels while keeping a predetermined width of main lobes. Thus, highly improved patterns with very deep sidelobe and increased directivity, with beam steering capabilities, are obtained.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123137181","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838936
S. El-Khamy, E. Sabry, S.H. Nour El-Din
Wavelet packet division multiple access (WPDMA) is a high capacity, flexible and robust orthogonal multiple access technique in which wavelet packet basis functions are chosen as the coding waveforms. By analogy with the frequency hopped communication scheme, incorporating the same technique into (WPDMA) schemes offers the potential for further performance improvements, especially for anti-jam communication and in frequency selective fading channels. We introduce bin-hopping wavelet packet division multiplexing (BH-WPDMA) schemes that exploit an efficient hopping structure. From the wavelet tree structured, it can be seen that once the scaling function and tree structures are chosen, all the basis functions are defined, therefore, we can "hop" the parameters of WPDMA. This structure provides performance and security improvement whilst retaining the capacity advantages and a number of desirable implementation features of WPDMA.
{"title":"Bin-hopping wavelet packet division multiple access (BH-WPDMA)","authors":"S. El-Khamy, E. Sabry, S.H. Nour El-Din","doi":"10.1109/NRSC.2000.838936","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838936","url":null,"abstract":"Wavelet packet division multiple access (WPDMA) is a high capacity, flexible and robust orthogonal multiple access technique in which wavelet packet basis functions are chosen as the coding waveforms. By analogy with the frequency hopped communication scheme, incorporating the same technique into (WPDMA) schemes offers the potential for further performance improvements, especially for anti-jam communication and in frequency selective fading channels. We introduce bin-hopping wavelet packet division multiplexing (BH-WPDMA) schemes that exploit an efficient hopping structure. From the wavelet tree structured, it can be seen that once the scaling function and tree structures are chosen, all the basis functions are defined, therefore, we can \"hop\" the parameters of WPDMA. This structure provides performance and security improvement whilst retaining the capacity advantages and a number of desirable implementation features of WPDMA.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125891260","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838974
N. G. Zaki, K. El-Shorbagy
The paper is concerned with investigation of the influence of an intense HF electric field and warm plasma waveguide on the electrostatic oscillations of a nonuniform bounded plasma. The stabilizing effect of a strong HF (pump) electrical field on a Buneman instability in a plane plasma waveguide is investigated. We use the separation method to solve the two-fluid plasma equations which describe the system. The method used enables us to determine the frequencies and growth rates of unstable modes and the self-consistent electrical field. Plasma elections are considered to have a thermal velocity. It is shown that the growth rate of the instability in a warm plasma is reduced compared to cold plasma. Also, it is found that the warmth of the plasma electrons has no effect on the solution of the space part of the problem.
{"title":"Suppression of Buneman instability by means of HF electric field in a warm plasma waveguide","authors":"N. G. Zaki, K. El-Shorbagy","doi":"10.1109/NRSC.2000.838974","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838974","url":null,"abstract":"The paper is concerned with investigation of the influence of an intense HF electric field and warm plasma waveguide on the electrostatic oscillations of a nonuniform bounded plasma. The stabilizing effect of a strong HF (pump) electrical field on a Buneman instability in a plane plasma waveguide is investigated. We use the separation method to solve the two-fluid plasma equations which describe the system. The method used enables us to determine the frequencies and growth rates of unstable modes and the self-consistent electrical field. Plasma elections are considered to have a thermal velocity. It is shown that the growth rate of the instability in a warm plasma is reduced compared to cold plasma. Also, it is found that the warmth of the plasma electrons has no effect on the solution of the space part of the problem.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122323506","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838901
S. El-Khamy, M. Aboul-Dahab
Fractal arrays are known for their self-similar performance in multi-band operation. A large number of elements in the array is a source of inconvenience in the realization procedure. In this paper, a technique is introduced for the simplification and size reduction of the Koch array. The fractal array factors presented keep the same shape at several bands because they are constructed from self-similar curves. A Kaiser window as a generating pulse function is proposed for the design of Koch-array factors. Kaiser windows are characterized by having the lowest side lobes of all windows in the transformed domain. Applying such a technique would result in an array current distribution having lower side lobes, with a reduced array size after setting a threshold beyond which the elements are eliminated. The resulting reduced array is then quantised for implementation purposes. This paper also compares the performance of reduced Koch arrays for multiband operation with their derivative Koch arrays.
{"title":"Simplifying and size reduction of Kaiser-Koch multiband fractal arrays using windowing and quantization techniques","authors":"S. El-Khamy, M. Aboul-Dahab","doi":"10.1109/NRSC.2000.838901","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838901","url":null,"abstract":"Fractal arrays are known for their self-similar performance in multi-band operation. A large number of elements in the array is a source of inconvenience in the realization procedure. In this paper, a technique is introduced for the simplification and size reduction of the Koch array. The fractal array factors presented keep the same shape at several bands because they are constructed from self-similar curves. A Kaiser window as a generating pulse function is proposed for the design of Koch-array factors. Kaiser windows are characterized by having the lowest side lobes of all windows in the transformed domain. Applying such a technique would result in an array current distribution having lower side lobes, with a reduced array size after setting a threshold beyond which the elements are eliminated. The resulting reduced array is then quantised for implementation purposes. This paper also compares the performance of reduced Koch arrays for multiband operation with their derivative Koch arrays.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132165820","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838929
A. Abdel-Hamid, M. Aboul-Dahab, W.M. Rabie
In a mobile communication environment the received signals are corrupted with noise in the communication channel. This noise can be modeled mathematically according to the channel characteristics by one of several channel models. In this paper, a channel model estimator based on the Chi-square test is presented. This estimator recognizes an appropriate statistical channel model based on the best matched probability distribution during the observed period. Computer simulation is used to examine the performance of this channel model estimator where data from several channel models have been tested. Satisfactory results have been obtained through this approach.
{"title":"Mobile channel model estimators and their performance evaluation using computer simulation","authors":"A. Abdel-Hamid, M. Aboul-Dahab, W.M. Rabie","doi":"10.1109/NRSC.2000.838929","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838929","url":null,"abstract":"In a mobile communication environment the received signals are corrupted with noise in the communication channel. This noise can be modeled mathematically according to the channel characteristics by one of several channel models. In this paper, a channel model estimator based on the Chi-square test is presented. This estimator recognizes an appropriate statistical channel model based on the best matched probability distribution during the observed period. Computer simulation is used to examine the performance of this channel model estimator where data from several channel models have been tested. Satisfactory results have been obtained through this approach.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"155 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132944068","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838905
M.A. Aboul Dahab, Mohamed M. M. Omar
Fully or partially adaptive antenna array (AAA) techniques are designed to reduce the effect of interference and jamming signals. This is done by automatically steering nulls in the array field pattern directed towards the direction of arrival of the interfering signal. We present two simple and easy-to-implement partially AAA techniques to eliminate the effect of interfering signal when its direction of arrival is known. The first technique is based upon controlling the amplitudes of the signals at the end-elements of the array. This is done via a proposed algorithm that adjusts the weights of these elements to take one of three preset values. The technique is suitable to steer a null only within the range of the first sidelobe of the array. The second technique utilizes an auxiliary parallel array composed of 2N elements and is capable of steering a deep null at the direction of any sidelobe. This is done by controlling the weight coefficients of all elements of the auxiliary array. A performance criterion is proposed which is based upon equal weight coefficients for all auxiliary elements. In this way, the array has one degree of freedom, i.e. capable of steering only one null in the direction of arrival of interference. Satisfactory results are obtained via computer simulation results of the two techniques.
{"title":"Two partially adaptive antenna array techniques for interference elimination","authors":"M.A. Aboul Dahab, Mohamed M. M. Omar","doi":"10.1109/NRSC.2000.838905","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838905","url":null,"abstract":"Fully or partially adaptive antenna array (AAA) techniques are designed to reduce the effect of interference and jamming signals. This is done by automatically steering nulls in the array field pattern directed towards the direction of arrival of the interfering signal. We present two simple and easy-to-implement partially AAA techniques to eliminate the effect of interfering signal when its direction of arrival is known. The first technique is based upon controlling the amplitudes of the signals at the end-elements of the array. This is done via a proposed algorithm that adjusts the weights of these elements to take one of three preset values. The technique is suitable to steer a null only within the range of the first sidelobe of the array. The second technique utilizes an auxiliary parallel array composed of 2N elements and is capable of steering a deep null at the direction of any sidelobe. This is done by controlling the weight coefficients of all elements of the auxiliary array. A performance criterion is proposed which is based upon equal weight coefficients for all auxiliary elements. In this way, the array has one degree of freedom, i.e. capable of steering only one null in the direction of arrival of interference. Satisfactory results are obtained via computer simulation results of the two techniques.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"1079 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133019075","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838849
A. Allam, A. Amein, F. Elghany
A MATHCAD code is developed for simulating the scatterer complex image for specific user requirements. The effect of the transmitted frequency is illustrated. The synthetic beamwidth, the chirp rate, and the scene size window are determined. These parameters impose some constraints or modifications on the transmitted signal from the synthetic aperture radar (SAR).
{"title":"Antenna synthetic beam imaging using chirp algorithm","authors":"A. Allam, A. Amein, F. Elghany","doi":"10.1109/NRSC.2000.838849","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838849","url":null,"abstract":"A MATHCAD code is developed for simulating the scatterer complex image for specific user requirements. The effect of the transmitted frequency is illustrated. The synthetic beamwidth, the chirp rate, and the scene size window are determined. These parameters impose some constraints or modifications on the transmitted signal from the synthetic aperture radar (SAR).","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130368264","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838968
H.I.M. Al Anwar, H. El Hennawy, E. Hashish, M. El Said Mostafa
A new proposed CAD method for the design of broadband microwave planar square law diode detectors is presented. In this method, the proposed broadband (low-Q) short circuit passive networks are used to contribute in diode matching. This method produces diode detectors with low VSWR over the useful broad bandwidth without using diode biasing (self bias) and without using resistance in the diode matching network. Examples of broadband square law Schottky barrier diode detectors designed using this method with their analysis are presented. These detectors have suitable topologies for realization using microstrip line or any other planar technology.
{"title":"A new proposed method for the design of broadband microwave planar diode detectors","authors":"H.I.M. Al Anwar, H. El Hennawy, E. Hashish, M. El Said Mostafa","doi":"10.1109/NRSC.2000.838968","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838968","url":null,"abstract":"A new proposed CAD method for the design of broadband microwave planar square law diode detectors is presented. In this method, the proposed broadband (low-Q) short circuit passive networks are used to contribute in diode matching. This method produces diode detectors with low VSWR over the useful broad bandwidth without using diode biasing (self bias) and without using resistance in the diode matching network. Examples of broadband square law Schottky barrier diode detectors designed using this method with their analysis are presented. These detectors have suitable topologies for realization using microstrip line or any other planar technology.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114975206","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 : 2000-02-22DOI: 10.1109/NRSC.2000.838838
A. Mahmoud, M.M. Abd Elrazzak, H. Elmikati
In this paper, rectangular microstrip patch antenna over a multi-layer substrate configuration is presented. This patch antenna configuration improves the bandwidth and the radiation pattern of the patch. The finite-difference time-domain (FDTD) method with perfectly matched layer absorber (PML) as well as Mur's (1981) first order absorbing boundary conditions (Mur's FOC) is applied to determine the return loss, the effective dielectric constant, the input impedance and the radiation pattern of the proposed structure. In addition, the effect of changing the air gap layer thickness of that antenna is studied. The results obtained by the FDTD with PML are found to be in better agreement with the published measured data than those obtained by the FDTD with Mur's FOC.
{"title":"FDTD analysis of patch antenna over a multi-layer substrate","authors":"A. Mahmoud, M.M. Abd Elrazzak, H. Elmikati","doi":"10.1109/NRSC.2000.838838","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838838","url":null,"abstract":"In this paper, rectangular microstrip patch antenna over a multi-layer substrate configuration is presented. This patch antenna configuration improves the bandwidth and the radiation pattern of the patch. The finite-difference time-domain (FDTD) method with perfectly matched layer absorber (PML) as well as Mur's (1981) first order absorbing boundary conditions (Mur's FOC) is applied to determine the return loss, the effective dielectric constant, the input impedance and the radiation pattern of the proposed structure. In addition, the effect of changing the air gap layer thickness of that antenna is studied. The results obtained by the FDTD with PML are found to be in better agreement with the published measured data than those obtained by the FDTD with Mur's FOC.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":"132 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113997499","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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