Pub Date : 2006-12-04DOI: 10.1109/INTLEC.2006.251663
S. Abe, M. Hirokawa, T. Zaitsu, T. Ninomiya
The power supply system which requires the low-voltage/high-current output has been changing from conventional centralized power system to distributed power system. The distributed power system consists of bus converter and POL. The most important factor is the system stability in bus architecture design. The overlap between the output impedance of bus converter and input impedance of POL causes system instability, and it has been an actual problem. Increasing the bus capacitor, system stability can be reduced easily. However, due to the limited space on the system board, increasing of bus capacitors is impractical. The urgent solution of the issue is desired strongly. This paper investigates the system stability by means of bus converter with peak current mode control to eliminate the output impedance peak. As a result, this system has sufficient stability margin due to the output impedance peak disappeared by means of peak current mode control
{"title":"Stability Comparison of Voltage Mode and Peak Current Mode Control for Bus Converter in On-Board Distributed Power System","authors":"S. Abe, M. Hirokawa, T. Zaitsu, T. Ninomiya","doi":"10.1109/INTLEC.2006.251663","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251663","url":null,"abstract":"The power supply system which requires the low-voltage/high-current output has been changing from conventional centralized power system to distributed power system. The distributed power system consists of bus converter and POL. The most important factor is the system stability in bus architecture design. The overlap between the output impedance of bus converter and input impedance of POL causes system instability, and it has been an actual problem. Increasing the bus capacitor, system stability can be reduced easily. However, due to the limited space on the system board, increasing of bus capacitors is impractical. The urgent solution of the issue is desired strongly. This paper investigates the system stability by means of bus converter with peak current mode control to eliminate the output impedance peak. As a result, this system has sufficient stability margin due to the output impedance peak disappeared by means of peak current mode control","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122776364","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251638
M. Hankaniemi, T. Suntio, M. Sippola
The paper investigates the load interactions in constant-current-controlled buck converters. The nominal transfer functions and the load interaction formalism are derived from the voltage-output-converter model by applying duality. It is observed that the constant-current control makes the converter very sensitive to load interactions implying that a proper controller design is a necessity. The high crossover frequency in the nominal control-to-output transfer function may lead to performance degradation if the initial control design is done with resistive load, because the typical load for constant-current controlled converters is a low impedance storage-battery recovering the nominal feature. It is shown that electronic loads, typically used in prototype testing and verification, might have unexpected characteristics. This may lead to wrong deductions of the converter stability and performance
{"title":"Analysis of the Load Interactions in Constant-Current-Controlled Buck Converter","authors":"M. Hankaniemi, T. Suntio, M. Sippola","doi":"10.1109/INTLEC.2006.251638","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251638","url":null,"abstract":"The paper investigates the load interactions in constant-current-controlled buck converters. The nominal transfer functions and the load interaction formalism are derived from the voltage-output-converter model by applying duality. It is observed that the constant-current control makes the converter very sensitive to load interactions implying that a proper controller design is a necessity. The high crossover frequency in the nominal control-to-output transfer function may lead to performance degradation if the initial control design is done with resistive load, because the typical load for constant-current controlled converters is a low impedance storage-battery recovering the nominal feature. It is shown that electronic loads, typically used in prototype testing and verification, might have unexpected characteristics. This may lead to wrong deductions of the converter stability and performance","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122888318","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251642
J. Brunarie, E. Olsson
This paper details the decision criteria and process to implement an innovative power system including new generation of rectifiers developed by Delta in combination with Saft Li-ion batteries in a major operator's mobile telecom network. This includes technical aspects such as application needs, product design and optimization, and validation of battery and rectifier choices. The paper describes the implementation of field tests and discusses the results of the trials. With the operator's major criterion being economical, the paper also includes a life cycle cost analysis of the battery/rectifier system in comparison to conventional systems equipped with VRLA. In conclusion, future perspectives of power system integration and lithium ion batteries are outlined
{"title":"High Energy Li-ion Batteries Combined with Compact Power Systems for Outdoor BTS: Technical and Economical Decision making from Field Test to Deployment","authors":"J. Brunarie, E. Olsson","doi":"10.1109/INTLEC.2006.251642","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251642","url":null,"abstract":"This paper details the decision criteria and process to implement an innovative power system including new generation of rectifiers developed by Delta in combination with Saft Li-ion batteries in a major operator's mobile telecom network. This includes technical aspects such as application needs, product design and optimization, and validation of battery and rectifier choices. The paper describes the implementation of field tests and discusses the results of the trials. With the operator's major criterion being economical, the paper also includes a life cycle cost analysis of the battery/rectifier system in comparison to conventional systems equipped with VRLA. In conclusion, future perspectives of power system integration and lithium ion batteries are outlined","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125024138","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251676
Alexis Kwasinski, P. Krein
This paper presents a systematic microgrid-based telecom power system configuration analysis to establish a possible basis for an optimal design. It compares several configurations using a value function that includes important telecommunication power plant characteristics, such as cost and availability. The comparison yields guidelines on how best to configure the system. Design choices studied include the system main bus voltage, redundancy policy, and the microsource configuration. The analysis indicates that microgrid-based telecom power systems outperform traditional telecom power plants for medium to high-power sites, such as switching centers, and gives similar results for cell sites and low power transmission nodes. Microgrid configurations with an approximate 156 V main dc bus voltage achieve a slightly higher value function than other evaluated options
{"title":"Optimal Configuration Analysis of a Microgrid-Based Telecom Power System","authors":"Alexis Kwasinski, P. Krein","doi":"10.1109/INTLEC.2006.251676","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251676","url":null,"abstract":"This paper presents a systematic microgrid-based telecom power system configuration analysis to establish a possible basis for an optimal design. It compares several configurations using a value function that includes important telecommunication power plant characteristics, such as cost and availability. The comparison yields guidelines on how best to configure the system. Design choices studied include the system main bus voltage, redundancy policy, and the microsource configuration. The analysis indicates that microgrid-based telecom power systems outperform traditional telecom power plants for medium to high-power sites, such as switching centers, and gives similar results for cell sites and low power transmission nodes. Microgrid configurations with an approximate 156 V main dc bus voltage achieve a slightly higher value function than other evaluated options","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128723127","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251591
S. Lansburg, J. McDowall
Nickel-metal hydride (Ni-MH) technology is often overlooked by telecom users who are considering advanced battery technologies. The paper details the characteristics of Saft's large-format Ni-MH technology and provides comparisons with nickel-cadmium, valve-regulated lead-acid and lithium-based batteries. It will be seen that Ni-MH offers a viable solution for certain niche applications in telecom power. One such niche is the emerging application for modular central office (CO) power. The paper describes this application and discusses the results of trials with a large operating company that is beginning to develop modular CO installations. While these large-format Ni-MH batteries are best applied in floating applications with controlled temperatures, this does not mean that Ni-MH electrochemistry is excluded from outside plant applications. Certain legacy digital loop carrier systems with distributed power have long been known to overcharge traditional batteries. Based on the space savings available with the use of high-temperature cylindrical Ni-MH cells, Saft has been able to integrate these cells with an innovative charging and control unit, all in the same space as existing VRLA batteries. This arrangement bypasses the damaging overcharging normally imposed by the installed charger, without affecting the attached loads, and allows the battery to reach its full life expectancy of over 8 years at a continuous operating temperature of 37 degC (100 degF). The last section of this paper describes the components of this battery system. The results of field trials and NEBS testing will also be discussed
{"title":"Nickel-Metal Hydride Technology- A Solution for Niche Telecom Power Applications","authors":"S. Lansburg, J. McDowall","doi":"10.1109/INTLEC.2006.251591","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251591","url":null,"abstract":"Nickel-metal hydride (Ni-MH) technology is often overlooked by telecom users who are considering advanced battery technologies. The paper details the characteristics of Saft's large-format Ni-MH technology and provides comparisons with nickel-cadmium, valve-regulated lead-acid and lithium-based batteries. It will be seen that Ni-MH offers a viable solution for certain niche applications in telecom power. One such niche is the emerging application for modular central office (CO) power. The paper describes this application and discusses the results of trials with a large operating company that is beginning to develop modular CO installations. While these large-format Ni-MH batteries are best applied in floating applications with controlled temperatures, this does not mean that Ni-MH electrochemistry is excluded from outside plant applications. Certain legacy digital loop carrier systems with distributed power have long been known to overcharge traditional batteries. Based on the space savings available with the use of high-temperature cylindrical Ni-MH cells, Saft has been able to integrate these cells with an innovative charging and control unit, all in the same space as existing VRLA batteries. This arrangement bypasses the damaging overcharging normally imposed by the installed charger, without affecting the attached loads, and allows the battery to reach its full life expectancy of over 8 years at a continuous operating temperature of 37 degC (100 degF). The last section of this paper describes the components of this battery system. The results of field trials and NEBS testing will also be discussed","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125846683","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251648
M. Youssef, P. Jain
This paper presents the first steps taken towards the design of the digitally controlled self-oscillating resonant voltage regulator modules (VRMs). The design steps are given in detail with the development of the equivalent SIMULINK model of the overall system. The design aims to enlarge the bandwidth of the converter via selecting the crossover frequency of the closed loop system. SIMULINK and preliminary analog-mixed prototype results are given to verify the proposed work
{"title":"A Wide Band-width Design of a Self-oscillating Resonant Converter via a Novel Discrete Time Model Criterion","authors":"M. Youssef, P. Jain","doi":"10.1109/INTLEC.2006.251648","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251648","url":null,"abstract":"This paper presents the first steps taken towards the design of the digitally controlled self-oscillating resonant voltage regulator modules (VRMs). The design steps are given in detail with the development of the equivalent SIMULINK model of the overall system. The design aims to enlarge the bandwidth of the converter via selecting the crossover frequency of the closed loop system. SIMULINK and preliminary analog-mixed prototype results are given to verify the proposed work","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116922805","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251649
W. Shireen, H. Nene
Fuel cells are one of the cleanest and most efficient technologies for generating electricity. In most cases, the fuel cell associated power conditioning system must include a DC-DC converter and a DC to AC inverter. Inverter input ripple current has been reported to possibly degrade fuel cell performance and reduce operating life if ripple currents are not adequately controlled. This paper proposes an active filtering method to cancel the 2nd harmonic current ripple drawn from the fuel cell source in a typical single phase fuel cell system. The proposed active harmonic filter provides an alternate path for the 120 Hz ripple, thereby, preventing the ripple from circulating through the source. The proposed system was simulated using PSpice and the results are presented. Experimental results from a laboratory prototype are also included to validate the proposed approach
{"title":"Active Filtering of Input Ripple Current to Obtain Efficient and Reliable Power from Fuel Cell Sources","authors":"W. Shireen, H. Nene","doi":"10.1109/INTLEC.2006.251649","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251649","url":null,"abstract":"Fuel cells are one of the cleanest and most efficient technologies for generating electricity. In most cases, the fuel cell associated power conditioning system must include a DC-DC converter and a DC to AC inverter. Inverter input ripple current has been reported to possibly degrade fuel cell performance and reduce operating life if ripple currents are not adequately controlled. This paper proposes an active filtering method to cancel the 2nd harmonic current ripple drawn from the fuel cell source in a typical single phase fuel cell system. The proposed active harmonic filter provides an alternate path for the 120 Hz ripple, thereby, preventing the ripple from circulating through the source. The proposed system was simulated using PSpice and the results are presented. Experimental results from a laboratory prototype are also included to validate the proposed approach","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"13 6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125630067","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251596
Lisheng Shi, Limin Chen, C. Yin
A novel zero voltage transition (ZVT) soft switching PWM converter is proposed in this paper and its' operation principle is analyzed in detail. Two of the novel converter topologies boost and buck circuits are given. Finally, the novel boost converter is used in power factor correction circuit successfully
{"title":"A Novel PWM Soft Switching DC-DC Converter","authors":"Lisheng Shi, Limin Chen, C. Yin","doi":"10.1109/INTLEC.2006.251596","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251596","url":null,"abstract":"A novel zero voltage transition (ZVT) soft switching PWM converter is proposed in this paper and its' operation principle is analyzed in detail. Two of the novel converter topologies boost and buck circuits are given. Finally, the novel boost converter is used in power factor correction circuit successfully","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129297853","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251607
J. Lam, K. Praveen
In this paper, a new modified valley fill circuit is proposed to combine with a half-bridge current source resonant inverter as the power circuit for a high power factor valley fill electronic ballast. The proposed circuit is capable to lower the discharge voltage of the valley fill capacitance by inserting another branch of valley fill capacitor in the original circuit. When the capacitors are connected in parallel, the voltage discharged across the capacitors is only one-third of the peak line voltage, which allows the conduction angle of the line current to be further extended so that a lower total harmonic distortion level can be achieved. Another advantage is that the smaller capacitance greatly reduces the current spike demanded at the peak line voltage when compared to the one seen in the conventional valley fill ballasts. The high crest factor problem is also eliminated in the proposed circuit as continuous variable frequency control is employed to continuously regulate the lamp current to stay within a steady envelope. Detailed explanations on the operating principles of the proposed circuit are provided in this paper. Simulation and experimental results are provided to validate with all the theoretical analysis for a 20 W compact fluorescent lamp
{"title":"A New Passive Valley Fill Dimming Electronic Ballast with Extended Line Current Conduction Angle","authors":"J. Lam, K. Praveen","doi":"10.1109/INTLEC.2006.251607","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251607","url":null,"abstract":"In this paper, a new modified valley fill circuit is proposed to combine with a half-bridge current source resonant inverter as the power circuit for a high power factor valley fill electronic ballast. The proposed circuit is capable to lower the discharge voltage of the valley fill capacitance by inserting another branch of valley fill capacitor in the original circuit. When the capacitors are connected in parallel, the voltage discharged across the capacitors is only one-third of the peak line voltage, which allows the conduction angle of the line current to be further extended so that a lower total harmonic distortion level can be achieved. Another advantage is that the smaller capacitance greatly reduces the current spike demanded at the peak line voltage when compared to the one seen in the conventional valley fill ballasts. The high crest factor problem is also eliminated in the proposed circuit as continuous variable frequency control is employed to continuously regulate the lamp current to stay within a steady envelope. Detailed explanations on the operating principles of the proposed circuit are provided in this paper. Simulation and experimental results are provided to validate with all the theoretical analysis for a 20 W compact fluorescent lamp","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134466269","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 : 2006-12-04DOI: 10.1109/INTLEC.2006.251610
R. Bibmeier
The continuous utilisability of transmitting/receiving systems and switching centres for mobile communications important. These influence the domain of private telecommunication directly by customer satisfaction, in the domain of professional mobile radio (PMR; e.g. public safety organisations), the continuous availability is in the foreground. With increased expansion and due to the high danger potential lightning protection and thus over voltage protection is becoming more relevant for cost-intensive engineering and the demand for permanent availability of the network operation are making surge protective devices (SPD) indispensable. The performance of such SPD has to fulfil the highest requirements. For use in cellular networks a lot of different mechanical and physical requirements are in demand. A combination of class I arresters, based on spark gap technology and class II arresters, based on MOV technology realise a protective device which combine a high absorption of energy and a fast response. This paper describes the requirements, which has to be fulfilled to realise an effective internal lightning protection system
{"title":"High demands on cellular networks-High demands on Surge Protective Devices","authors":"R. Bibmeier","doi":"10.1109/INTLEC.2006.251610","DOIUrl":"https://doi.org/10.1109/INTLEC.2006.251610","url":null,"abstract":"The continuous utilisability of transmitting/receiving systems and switching centres for mobile communications important. These influence the domain of private telecommunication directly by customer satisfaction, in the domain of professional mobile radio (PMR; e.g. public safety organisations), the continuous availability is in the foreground. With increased expansion and due to the high danger potential lightning protection and thus over voltage protection is becoming more relevant for cost-intensive engineering and the demand for permanent availability of the network operation are making surge protective devices (SPD) indispensable. The performance of such SPD has to fulfil the highest requirements. For use in cellular networks a lot of different mechanical and physical requirements are in demand. A combination of class I arresters, based on spark gap technology and class II arresters, based on MOV technology realise a protective device which combine a high absorption of energy and a fast response. This paper describes the requirements, which has to be fulfilled to realise an effective internal lightning protection system","PeriodicalId":356699,"journal":{"name":"INTELEC 06 - Twenty-Eighth International Telecommunications Energy Conference","volume":"182 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134013734","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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