Pub Date : 2000-04-04DOI: 10.1109/DRPT.2000.855687
R. Teive, F. Silveira, M. Filho
This paper describes a decision support system (DSS) based on an expert system (ES), which aids the user to select feasible projects among a strategic portfolio supplied by a dynamic simulator. The purpose of developing a DSS embedded in an ES structure, is to search for the modelling of the decision-maker rather than the decision process. Thus, the ES stores not only the expertise of the utility engineers, but some knowledge about the company goals. The dynamic simulator (DS) was developed by using the system dynamics paradigm, allowing the simulation of investment policies, taking into account the dynamic behavior of the involved variables and assuming that the decisions are taken continuously, leading to continuous actions. The proposed DSS is integrated with a strategic database (SDB), which contains information about competitors, regulatory system, special consumers and the energy wholesale market in general, forming an integrated computational system. The ES manages the integration between the DSS and the SDB, retrieving the information necessary to the simulation in progress.
{"title":"A strategic decision support system for an electric utility company in a competitive environment","authors":"R. Teive, F. Silveira, M. Filho","doi":"10.1109/DRPT.2000.855687","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855687","url":null,"abstract":"This paper describes a decision support system (DSS) based on an expert system (ES), which aids the user to select feasible projects among a strategic portfolio supplied by a dynamic simulator. The purpose of developing a DSS embedded in an ES structure, is to search for the modelling of the decision-maker rather than the decision process. Thus, the ES stores not only the expertise of the utility engineers, but some knowledge about the company goals. The dynamic simulator (DS) was developed by using the system dynamics paradigm, allowing the simulation of investment policies, taking into account the dynamic behavior of the involved variables and assuming that the decisions are taken continuously, leading to continuous actions. The proposed DSS is integrated with a strategic database (SDB), which contains information about competitors, regulatory system, special consumers and the energy wholesale market in general, forming an integrated computational system. The ES manages the integration between the DSS and the SDB, retrieving the information necessary to the simulation in progress.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131114720","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855710
H. Marmiroli, H. Suzuki
This paper describes a business transaction model and the Internet-based information architecture for the open electricity market. A power exchange is assumed to coordinate and manage the trade of energy and ancillary services in the day-ahead market through the Internet infrastructure. Indispensable characteristics for the exchange mechanism are efficiency, transparency and equitability; in order to guarantee these requirements we introduce an optimization process operated by the power exchange which ensures an appropriate evaluation of the generation offers for the available resources under some operational constraints. Further, in this paper, a market simulation approach is described. Several agents are developed to simulate offer strategies. Each agent automatically analyzes market information, and based on its own characteristic, submits an offer to the power exchange. The simulator can be utilized as a decision-making tool for market participants. The system is implemented utilizing JAVA distribution architecture, such as Web technologies and JAVA servlets.
{"title":"Web-based framework for electricity market","authors":"H. Marmiroli, H. Suzuki","doi":"10.1109/DRPT.2000.855710","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855710","url":null,"abstract":"This paper describes a business transaction model and the Internet-based information architecture for the open electricity market. A power exchange is assumed to coordinate and manage the trade of energy and ancillary services in the day-ahead market through the Internet infrastructure. Indispensable characteristics for the exchange mechanism are efficiency, transparency and equitability; in order to guarantee these requirements we introduce an optimization process operated by the power exchange which ensures an appropriate evaluation of the generation offers for the available resources under some operational constraints. Further, in this paper, a market simulation approach is described. Several agents are developed to simulate offer strategies. Each agent automatically analyzes market information, and based on its own characteristic, submits an offer to the power exchange. The simulator can be utilized as a decision-making tool for market participants. The system is implemented utilizing JAVA distribution architecture, such as Web technologies and JAVA servlets.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115962019","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855632
N. Schnurr, T. Weber, W.H. Wellssow, T. Wess
On the basis of the increasing importance of the exchange of electrical energy between partners in an interconnected power system, the use of FACTS devices to control power transits is examined. The exact derivation of the necessary control values for the FACTS devices is presented with generally valid equations especially for long lines and weakly meshed power systems. The important influence of the available reactive power is also discussed for these cases. Finally various transeuropean transit scenarios are examined in a model of the eastern European power system. Nonconducted power transits are compared with the direct and the indirect conduction method and the results of load flow calculations allow an assessment of these methods of conducting power transits.
{"title":"Load-flow control with FACTS devices in competitive markets","authors":"N. Schnurr, T. Weber, W.H. Wellssow, T. Wess","doi":"10.1109/DRPT.2000.855632","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855632","url":null,"abstract":"On the basis of the increasing importance of the exchange of electrical energy between partners in an interconnected power system, the use of FACTS devices to control power transits is examined. The exact derivation of the necessary control values for the FACTS devices is presented with generally valid equations especially for long lines and weakly meshed power systems. The important influence of the available reactive power is also discussed for these cases. Finally various transeuropean transit scenarios are examined in a model of the eastern European power system. Nonconducted power transits are compared with the direct and the indirect conduction method and the results of load flow calculations allow an assessment of these methods of conducting power transits.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127749116","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855722
A. Hu, T. Lie, H. Gooi
A real time pricing (RTP) system is implemented in more and more countries. For customers, there exist some factors, which affect the benefits that can be obtained under the RTP system. One of these factors is the load forecast. Thus, a method of using the fuzzy logic technique for the customers to forecast load under the RTP system is proposed in this paper. Some digital simulation studies and related analyses are presented.
{"title":"Load forecast for customers under real time pricing systems","authors":"A. Hu, T. Lie, H. Gooi","doi":"10.1109/DRPT.2000.855722","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855722","url":null,"abstract":"A real time pricing (RTP) system is implemented in more and more countries. For customers, there exist some factors, which affect the benefits that can be obtained under the RTP system. One of these factors is the load forecast. Thus, a method of using the fuzzy logic technique for the customers to forecast load under the RTP system is proposed in this paper. Some digital simulation studies and related analyses are presented.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127534349","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855663
W. Luan, K. L. Lo, Y.X. Yu
Security assessment is to predict a power system's ability to withstand a set of next contingencies. An ANN-based pattern recognition method is used to perform static security assessment for power systems due to its potential in terms of speed and accuracy for online application. With the input pattern for ANN be composed of power system pre-contingency state described in busbar power injections (P, Q), the output pattern of ANN is composed of the performance index (PI) values of power system post-contingency state to a list of next contingencies. So the output vectors of ANN will indicate not only either 'secure' or 'insecure' state of the current system but also the severity of security limit violations under contingencies. To cope with the curse of dimensionality and improve efficiency of ANN, R-ReliefF algorithm is introduced to extract those variables that are with more discriminatory information from (P, Q) set to realise the nonlinear mapping from input space to output space. The proposed algorithm is tested on a 77-busbar practical power system with promising results.
{"title":"ANN-based pattern recognition technique for power system security assessment","authors":"W. Luan, K. L. Lo, Y.X. Yu","doi":"10.1109/DRPT.2000.855663","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855663","url":null,"abstract":"Security assessment is to predict a power system's ability to withstand a set of next contingencies. An ANN-based pattern recognition method is used to perform static security assessment for power systems due to its potential in terms of speed and accuracy for online application. With the input pattern for ANN be composed of power system pre-contingency state described in busbar power injections (P, Q), the output pattern of ANN is composed of the performance index (PI) values of power system post-contingency state to a list of next contingencies. So the output vectors of ANN will indicate not only either 'secure' or 'insecure' state of the current system but also the severity of security limit violations under contingencies. To cope with the curse of dimensionality and improve efficiency of ANN, R-ReliefF algorithm is introduced to extract those variables that are with more discriminatory information from (P, Q) set to realise the nonlinear mapping from input space to output space. The proposed algorithm is tested on a 77-busbar practical power system with promising results.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"136 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133785198","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855674
S. Salman, I. Rida
Voltage magnitude of distribution networks is usually maintained within statutory limits by using on load tap changer transformers that are controlled by automatic voltage control (AVC) relays. Traditional AVC relay is usually equipped with compounding whose settings are chosen in such away to compensate for the voltage drop along the feeder(s) emanating from source substation. This paper presents an attempt to design an AVC relay based on the application of artificial neural networks (ANNs). The input data file used for the training of the proposed AVC relay is prepared using a power system load flow program, which is written in FORTRAN. In this paper the structure of the proposed ANN-based AVC relay is presented and the test results that show its performance are also presented and discussed.
{"title":"ANN-based AVC relay for voltage control of distribution network with and without embedded generation","authors":"S. Salman, I. Rida","doi":"10.1109/DRPT.2000.855674","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855674","url":null,"abstract":"Voltage magnitude of distribution networks is usually maintained within statutory limits by using on load tap changer transformers that are controlled by automatic voltage control (AVC) relays. Traditional AVC relay is usually equipped with compounding whose settings are chosen in such away to compensate for the voltage drop along the feeder(s) emanating from source substation. This paper presents an attempt to design an AVC relay based on the application of artificial neural networks (ANNs). The input data file used for the training of the proposed AVC relay is prepared using a power system load flow program, which is written in FORTRAN. In this paper the structure of the proposed ANN-based AVC relay is presented and the test results that show its performance are also presented and discussed.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116835552","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855666
J. Rolim, C. R. da Silva Filho
This paper presents an expert system developed for a distribution company with the intention of helping the engineer responsible for the requests for equipment outage for preventive maintenance or network expansion. Usually, in order to decide whether these requests should be approved or not, the engineer verifies the possibility of transferring the load during outage considering constraints, such as which and what kind of consumers will be affected by the service, and whether they should be warned about the interruption, or if the timing is inadequate for them, etc.. The support of an intelligent system will allow the engineer to consider many other aspects, for instance, whether it is possible to join two requests in one interruption and, specially, to monitor the reliability indices of the area when the service under analysis is performed. The main objective is to minimise the frequency and duration of interruptions for preventive maintenance avoiding penalties from the regulatory agency.
{"title":"An intelligent tool for maintenance scheduling of distribution systems","authors":"J. Rolim, C. R. da Silva Filho","doi":"10.1109/DRPT.2000.855666","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855666","url":null,"abstract":"This paper presents an expert system developed for a distribution company with the intention of helping the engineer responsible for the requests for equipment outage for preventive maintenance or network expansion. Usually, in order to decide whether these requests should be approved or not, the engineer verifies the possibility of transferring the load during outage considering constraints, such as which and what kind of consumers will be affected by the service, and whether they should be warned about the interruption, or if the timing is inadequate for them, etc.. The support of an intelligent system will allow the engineer to consider many other aspects, for instance, whether it is possible to join two requests in one interruption and, specially, to monitor the reliability indices of the area when the service under analysis is performed. The main objective is to minimise the frequency and duration of interruptions for preventive maintenance avoiding penalties from the regulatory agency.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115737706","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855633
S.N. Singh, A. David
FACTS devices such as thyristor controlled series compensators and thyristor controlled phase angle regulators, by controlling the power flows in the network, can help to reduce the flows in heavily loaded lines resulting in an increased loadability of the network and reduced cost of production. Congestion management using FACTS devices requires a two step approach. First, the optimal location of these devices in the network must be ascertained and then, the settings of their control parameters optimised. This paper presents the development of simple and efficient models for optimal location of FACTS devices that can be used for congestion management by controlling their parameters optimally. Three different objectives have been considered and the results are compared. The effectiveness of the purposed methods is demonstrated on a 5-bus system and a 75-bus Indian system.
{"title":"Congestion management by optimising FACTS device location","authors":"S.N. Singh, A. David","doi":"10.1109/DRPT.2000.855633","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855633","url":null,"abstract":"FACTS devices such as thyristor controlled series compensators and thyristor controlled phase angle regulators, by controlling the power flows in the network, can help to reduce the flows in heavily loaded lines resulting in an increased loadability of the network and reduced cost of production. Congestion management using FACTS devices requires a two step approach. First, the optimal location of these devices in the network must be ascertained and then, the settings of their control parameters optimised. This paper presents the development of simple and efficient models for optimal location of FACTS devices that can be used for congestion management by controlling their parameters optimally. Three different objectives have been considered and the results are compared. The effectiveness of the purposed methods is demonstrated on a 5-bus system and a 75-bus Indian system.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127246462","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855640
J. Nicolaisen, C. Richter, Gerald B. SheblC
Successful operation and bidding in the competitive electricity marketplace requires well-planned strategies. The appropriate strategy is dependent on the state of the system. Much data (including time series) is available, and a proper analysis of this data can provide insight in choosing the right strategies. Traditional data analysis techniques can be time consuming. Techniques that quickly analyze the data can assist in forecasting price and demand and identifying the present state of the market, which should help the savvy trader in reacting intelligently to the market before its competitors. Advanced data analysis techniques may reveal patterns in the data that may be very helpful in forecasting demand or price. This paper compares several techniques that may help in identifying useful patterns in relevant time series data. These patterns are keys or leading indicators of future electric utility price or demand of electricity. The importance of quickly identifying these signals will increase as competition increases. The techniques being investigated are Fourier and Hartley transforms, line spectrum analysis using both Fourier transforms and Hartley transforms.
{"title":"Price signal analysis for competitive electric generation companies","authors":"J. Nicolaisen, C. Richter, Gerald B. SheblC","doi":"10.1109/DRPT.2000.855640","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855640","url":null,"abstract":"Successful operation and bidding in the competitive electricity marketplace requires well-planned strategies. The appropriate strategy is dependent on the state of the system. Much data (including time series) is available, and a proper analysis of this data can provide insight in choosing the right strategies. Traditional data analysis techniques can be time consuming. Techniques that quickly analyze the data can assist in forecasting price and demand and identifying the present state of the market, which should help the savvy trader in reacting intelligently to the market before its competitors. Advanced data analysis techniques may reveal patterns in the data that may be very helpful in forecasting demand or price. This paper compares several techniques that may help in identifying useful patterns in relevant time series data. These patterns are keys or leading indicators of future electric utility price or demand of electricity. The importance of quickly identifying these signals will increase as competition increases. The techniques being investigated are Fourier and Hartley transforms, line spectrum analysis using both Fourier transforms and Hartley transforms.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"136 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123522977","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 : 2000-04-04DOI: 10.1109/DRPT.2000.855688
Houmin Yan, Houzhong Yan, Hanqin Zhang
In this paper, the problem of optimal demand allocation in deregulated California energy markets is studied. Recently, this commodity has been deregulated into multiple time sequential markets, known as the block forward, the PX day-ahead and day off, and the ISO real-time energy markets. After deregulation, energy purchasers have to purchase energy on an hourly basis. It is challenging to allocate demand in the above energy markets in an optimal fashion. By using a stochastic dynamic programming technique in this study, the problem is resolved and an optimal solution is obtained. The authors derive the optimal demand allocation criterion. With the optimal allocation measurement, it is possible to provide efficient algorithms to divide demand at these time sequential markets.
{"title":"Demand allocation analysis for energy purchasers in deregulated energy markets","authors":"Houmin Yan, Houzhong Yan, Hanqin Zhang","doi":"10.1109/DRPT.2000.855688","DOIUrl":"https://doi.org/10.1109/DRPT.2000.855688","url":null,"abstract":"In this paper, the problem of optimal demand allocation in deregulated California energy markets is studied. Recently, this commodity has been deregulated into multiple time sequential markets, known as the block forward, the PX day-ahead and day off, and the ISO real-time energy markets. After deregulation, energy purchasers have to purchase energy on an hourly basis. It is challenging to allocate demand in the above energy markets in an optimal fashion. By using a stochastic dynamic programming technique in this study, the problem is resolved and an optimal solution is obtained. The authors derive the optimal demand allocation criterion. With the optimal allocation measurement, it is possible to provide efficient algorithms to divide demand at these time sequential markets.","PeriodicalId":127287,"journal":{"name":"DRPT2000. International Conference on Electric Utility Deregulation and Restructuring and Power Technologies. Proceedings (Cat. No.00EX382)","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121530736","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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