Pub Date : 2000-01-24DOI: 10.1109/RAMS.2000.816295
V. Loll
When large hardware-software systems are run-in or an acceptance testing is made, a problem is when to stop the test and deliver/accept the system. The same problem exists when a large software program is tested with simulated operations data. Based on two theses from the Technical University of Denmark, the paper describes and evaluates 7 possible algorithms. Of these algorithms, the three most promising are tested with simulated data. 27 different systems are simulated, and 50 Monte Carlo simulations made on each system. The stop times generated by the algorithm is compared with the known perfect stop time. Of the three algorithms two is selected as good. These two algorithms are then tested on 10 sets of real data. The algorithms are tested with three different levels of confidence. The number of correct and wrong stop decisions are counted. The conclusion is that the Weibull algorithm with 90% confidence level takes the right decision in every one of the 10 cases.
{"title":"Developing and testing algorithms for stopping testing, screening, run-in of large systems or programs","authors":"V. Loll","doi":"10.1109/RAMS.2000.816295","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816295","url":null,"abstract":"When large hardware-software systems are run-in or an acceptance testing is made, a problem is when to stop the test and deliver/accept the system. The same problem exists when a large software program is tested with simulated operations data. Based on two theses from the Technical University of Denmark, the paper describes and evaluates 7 possible algorithms. Of these algorithms, the three most promising are tested with simulated data. 27 different systems are simulated, and 50 Monte Carlo simulations made on each system. The stop times generated by the algorithm is compared with the known perfect stop time. Of the three algorithms two is selected as good. These two algorithms are then tested on 10 sets of real data. The algorithms are tested with three different levels of confidence. The number of correct and wrong stop decisions are counted. The conclusion is that the Weibull algorithm with 90% confidence level takes the right decision in every one of the 10 cases.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130455370","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816279
D. Crowe
Embarking on an extensive program of reliability science will provide a company with a long-term value add proposition, setting it apart from it competitors, returning many times over the value of that investment. It must be noted that this process requires having a long-term commitment to build and support a world-class reliability operation, the fruits of which are often not seen in real time. The operation can be extensive in cost but the gains can be great. Engineers must always understand the return on investment.
{"title":"Reliability in today's business environment","authors":"D. Crowe","doi":"10.1109/RAMS.2000.816279","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816279","url":null,"abstract":"Embarking on an extensive program of reliability science will provide a company with a long-term value add proposition, setting it apart from it competitors, returning many times over the value of that investment. It must be noted that this process requires having a long-term commitment to build and support a world-class reliability operation, the fruits of which are often not seen in real time. The operation can be extensive in cost but the gains can be great. Engineers must always understand the return on investment.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128624207","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816335
R. J. Mulvihill, F.M. Safie
The current Space Shuttle external tank design is called the super light weight tank (SLWT). A weight reduction of approximately 30% was achieved relative to the prior design called the light weight tank (LWT). The new NASA risk assessment tool, the quantitative risk assessment system (QRAS), was used to compare the risk of the two designs. The comparison includes consideration of the apparent reduction of the design safety factor for SLWT welds when a weld repair is required. The risk models for the structural failure accident scenario include five initiating events (IEs): (1) liquid oxygen (LO2) tank component failure; (2) liquid hydrogen (LH2) tank component failure; (3) LO2 tank weld failure; (4) LH2 tank weld failure; and (5) intertank failure. Although the risk results for the LH2 and LO2 tank welds for IEs 2 and 4 are higher for the SLWT vs. the LWT, the reverse is true for tank components IEs 1, 3 and 5. The SLWT has a slightly lower risk of structural failure. The impact of this difference is not significant to the total risk when the other six scenarios are also included.
{"title":"Application of the NASA risk assessment tool to the evaluation of the Space Shuttle external tank re-welding process","authors":"R. J. Mulvihill, F.M. Safie","doi":"10.1109/RAMS.2000.816335","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816335","url":null,"abstract":"The current Space Shuttle external tank design is called the super light weight tank (SLWT). A weight reduction of approximately 30% was achieved relative to the prior design called the light weight tank (LWT). The new NASA risk assessment tool, the quantitative risk assessment system (QRAS), was used to compare the risk of the two designs. The comparison includes consideration of the apparent reduction of the design safety factor for SLWT welds when a weld repair is required. The risk models for the structural failure accident scenario include five initiating events (IEs): (1) liquid oxygen (LO2) tank component failure; (2) liquid hydrogen (LH2) tank component failure; (3) LO2 tank weld failure; (4) LH2 tank weld failure; and (5) intertank failure. Although the risk results for the LH2 and LO2 tank welds for IEs 2 and 4 are higher for the SLWT vs. the LWT, the reverse is true for tank components IEs 1, 3 and 5. The SLWT has a slightly lower risk of structural failure. The impact of this difference is not significant to the total risk when the other six scenarios are also included.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134457665","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816286
J. Elerath
Most commercial enterprises want a meaningful yet simple method for determining product reliability. "Average", "annual" or "annualized" failure rates are selected because of their apparent simplicity. All involve some sort of "failure rate" averaging over some period of time. All are abbreviated AFR even though there are no accepted industry standard definitions for these terms or the processes and conditions for their measurement. If the failure rate is not constant in time, creating an average can easily generate meaningless results. A number of businesses use the term "failure rate" but are in fact calculating probabilities or time independent percentages. A basic premise for this paper is that the true underlying product failure rates are not constant in time. This paper presents a detailed discussion of different ways commercial industries calculate simple failure rate based metrics. It identifies some ambiguities in the definitions and resultant inaccuracies. It will help the reliability pundit understand the mathematical considerations, making him more aware of potential problems. This paper should help generalists and managers understand that the AFR's they calculate may be significantly different than those calculated by their suppliers and customers. This can result in substantially different numbers and conclusions. Averaging instantaneous failure rates should be done only to smooth data collected from a distribution known to have a constant failure rate.
{"title":"AFR: problems of definition, calculation and measurement in a commercial environment","authors":"J. Elerath","doi":"10.1109/RAMS.2000.816286","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816286","url":null,"abstract":"Most commercial enterprises want a meaningful yet simple method for determining product reliability. \"Average\", \"annual\" or \"annualized\" failure rates are selected because of their apparent simplicity. All involve some sort of \"failure rate\" averaging over some period of time. All are abbreviated AFR even though there are no accepted industry standard definitions for these terms or the processes and conditions for their measurement. If the failure rate is not constant in time, creating an average can easily generate meaningless results. A number of businesses use the term \"failure rate\" but are in fact calculating probabilities or time independent percentages. A basic premise for this paper is that the true underlying product failure rates are not constant in time. This paper presents a detailed discussion of different ways commercial industries calculate simple failure rate based metrics. It identifies some ambiguities in the definitions and resultant inaccuracies. It will help the reliability pundit understand the mathematical considerations, making him more aware of potential problems. This paper should help generalists and managers understand that the AFR's they calculate may be significantly different than those calculated by their suppliers and customers. This can result in substantially different numbers and conclusions. Averaging instantaneous failure rates should be done only to smooth data collected from a distribution known to have a constant failure rate.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124525914","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816287
Ming-Wei Lu, R. Rudy
An automotive company's goal is to design and manufacture vehicles that will meet the needs and the expectations of the customers. It is essential for the design engineer to understand and take into account all sources of variation, which will be encountered by the system or component being developed. In this paper, the methods of derivation for the reliability test target requirement (at 95/sup th/ percentile customer usage severity level) from a given field target requirement (in C/100) is described. Formulas are derived under the assumption that both stress and strength are normally distributed, lognormally distributed, and Weibull distributed.
{"title":"Reliability test target development","authors":"Ming-Wei Lu, R. Rudy","doi":"10.1109/RAMS.2000.816287","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816287","url":null,"abstract":"An automotive company's goal is to design and manufacture vehicles that will meet the needs and the expectations of the customers. It is essential for the design engineer to understand and take into account all sources of variation, which will be encountered by the system or component being developed. In this paper, the methods of derivation for the reliability test target requirement (at 95/sup th/ percentile customer usage severity level) from a given field target requirement (in C/100) is described. Formulas are derived under the assumption that both stress and strength are normally distributed, lognormally distributed, and Weibull distributed.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126711426","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816306
J. Elerath
Great strides have been made in creating a more realistic method for specifying disk drive reliability in a competitive commercial environment. Mean time between (before) failure (MTBF) is misleading and causes great conflict between drive manufacturers and drive integrators. The single most prominent cause is that the failure distribution for disk drives is not exponential during the first year of product use. To rectify this problem, drive hazard rate, in the form of a stair-step approximation to the Weibull, has been instituted as a standard way of representing reliability in the disk drive industry. Although not problem free, this method for specifying reliability is more easily correlated to field experience and can be used to more accurately calculate the expected number of returns and spares needed.
{"title":"Specifying reliability in the disk drive industry: No more MTBF's","authors":"J. Elerath","doi":"10.1109/RAMS.2000.816306","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816306","url":null,"abstract":"Great strides have been made in creating a more realistic method for specifying disk drive reliability in a competitive commercial environment. Mean time between (before) failure (MTBF) is misleading and causes great conflict between drive manufacturers and drive integrators. The single most prominent cause is that the failure distribution for disk drives is not exponential during the first year of product use. To rectify this problem, drive hazard rate, in the form of a stair-step approximation to the Weibull, has been instituted as a standard way of representing reliability in the disk drive industry. Although not problem free, this method for specifying reliability is more easily correlated to field experience and can be used to more accurately calculate the expected number of returns and spares needed.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131953420","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816321
M. Kaminskiy, Vasiliy V. Krivtsov
A brief overview of the statistical aspects of warranty prediction is given as an introduction. The main discussion then focuses on warranty claim prediction for repairable products. Introduced by Kijima and Sumita (1986), a g-renewal process (GRP) can be considered as a model for major repair assumptions encountered in repairable product reliability analysis. These assumptions include "good-as-new", "same-as-old", the intermediate "better-than-old-but-worse-than-new", and "worse-than-old". A statistical procedure is developed for estimation of the GRP parameter, which is suggested to have engineering meaning of the effectiveness of the repair actions. A practical example of the GRP application in statistical warranty prediction is given as an illustration of the proposed estimation method. The paper arrives to the following conclusions: The GRP provides high flexibility in modeling real life failure occurrence processes by covering major repair assumptions encountered in practice. A Monte Carlo simulation can be considered as a method for statistical estimation of the GRP. Warranty claim prediction based on GRP provides a higher accuracy compared to the ORP or the NHPP.
{"title":"G-renewal process as a model for statistical warranty claim prediction","authors":"M. Kaminskiy, Vasiliy V. Krivtsov","doi":"10.1109/RAMS.2000.816321","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816321","url":null,"abstract":"A brief overview of the statistical aspects of warranty prediction is given as an introduction. The main discussion then focuses on warranty claim prediction for repairable products. Introduced by Kijima and Sumita (1986), a g-renewal process (GRP) can be considered as a model for major repair assumptions encountered in repairable product reliability analysis. These assumptions include \"good-as-new\", \"same-as-old\", the intermediate \"better-than-old-but-worse-than-new\", and \"worse-than-old\". A statistical procedure is developed for estimation of the GRP parameter, which is suggested to have engineering meaning of the effectiveness of the repair actions. A practical example of the GRP application in statistical warranty prediction is given as an illustration of the proposed estimation method. The paper arrives to the following conclusions: The GRP provides high flexibility in modeling real life failure occurrence processes by covering major repair assumptions encountered in practice. A Monte Carlo simulation can be considered as a method for statistical estimation of the GRP. Warranty claim prediction based on GRP provides a higher accuracy compared to the ORP or the NHPP.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133099034","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816282
S. Vikman, A. Lonnqvist
A recent nationwide survey to the Swedish Engineering Industry disclosed that the understanding and use of reliability and safety methods by the small and medium sized companies on an average was distressingly low. Less than 30% of the smaller companies were familiar with reliability. In 1996, based on a survey and a following "out-line study", a new project was initiated by the Association of Swedish Engineering Industries, VI, and its Reliability Committee Te 5/2. The goal was to develop and document a program for "cooperative reliability development by small and medium-sized companies of the Swedish industrial sector". It will offer help to companies to initiate need based and local reliability work/activities. Starting point is an auditing/review of a company's existent process(es) and an audit of existing reliability status. Based on this, one will reach an understanding of in what way any "down-to-the-floor" simplified reliability-centered activity could be helpful. The final program will include necessary information and methods packages, training activities, expertise for managerial support and guidance during start-up and access to consultancy support where necessary for further implementation. This paper describes the project and its findings and illustrates the tools and methods developed for organizing individual down-to-the-floor reliability work programs by the industry.
{"title":"A reliability development program for the Swedish industry","authors":"S. Vikman, A. Lonnqvist","doi":"10.1109/RAMS.2000.816282","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816282","url":null,"abstract":"A recent nationwide survey to the Swedish Engineering Industry disclosed that the understanding and use of reliability and safety methods by the small and medium sized companies on an average was distressingly low. Less than 30% of the smaller companies were familiar with reliability. In 1996, based on a survey and a following \"out-line study\", a new project was initiated by the Association of Swedish Engineering Industries, VI, and its Reliability Committee Te 5/2. The goal was to develop and document a program for \"cooperative reliability development by small and medium-sized companies of the Swedish industrial sector\". It will offer help to companies to initiate need based and local reliability work/activities. Starting point is an auditing/review of a company's existent process(es) and an audit of existing reliability status. Based on this, one will reach an understanding of in what way any \"down-to-the-floor\" simplified reliability-centered activity could be helpful. The final program will include necessary information and methods packages, training activities, expertise for managerial support and guidance during start-up and access to consultancy support where necessary for further implementation. This paper describes the project and its findings and illustrates the tools and methods developed for organizing individual down-to-the-floor reliability work programs by the industry.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114299801","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816288
M. Morelli
Benchmarking has been very instrumental to Otis Elevator Company's introduction and continual improvement of several key reliability engineering activities. The feasibility of using the highly accelerated life testing and highly accelerated stress screening methods for electronics' reliability testing were studied and implemented in part by benchmarking with other companies already practising the techniques and have been continually improved using another benchmarking arrangement. Failure modes and effects analysis methods were also studied by benchmarking with other companies and attending several "outside" training courses. Activities such as part burn-in and reliability prediction were eliminated after benchmarking and analyses were performed.
{"title":"Using benchmarking to introduce and improve reliability engineering","authors":"M. Morelli","doi":"10.1109/RAMS.2000.816288","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816288","url":null,"abstract":"Benchmarking has been very instrumental to Otis Elevator Company's introduction and continual improvement of several key reliability engineering activities. The feasibility of using the highly accelerated life testing and highly accelerated stress screening methods for electronics' reliability testing were studied and implemented in part by benchmarking with other companies already practising the techniques and have been continually improved using another benchmarking arrangement. Failure modes and effects analysis methods were also studied by benchmarking with other companies and attending several \"outside\" training courses. Activities such as part burn-in and reliability prediction were eliminated after benchmarking and analyses were performed.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114632546","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 : 2000-01-24DOI: 10.1109/RAMS.2000.816300
V. Crk
The importance of degradation analysis as a method of assessing the reliability of highly reliable components and systems constantly increases due to the continuous efforts of the manufacturers to produce more and more reliable products. The presented methodology is an effective way to estimate the system's reliability by monitoring performance degradation. Its advantage is that the times to failure are not directly observed but the degradation that can be accurately measured. Consequently, the test time can be significantly shorter than if the times to failure are recorded.
{"title":"Reliability assessment from degradation data","authors":"V. Crk","doi":"10.1109/RAMS.2000.816300","DOIUrl":"https://doi.org/10.1109/RAMS.2000.816300","url":null,"abstract":"The importance of degradation analysis as a method of assessing the reliability of highly reliable components and systems constantly increases due to the continuous efforts of the manufacturers to produce more and more reliable products. The presented methodology is an effective way to estimate the system's reliability by monitoring performance degradation. Its advantage is that the times to failure are not directly observed but the degradation that can be accurately measured. Consequently, the test time can be significantly shorter than if the times to failure are recorded.","PeriodicalId":178321,"journal":{"name":"Annual Reliability and Maintainability Symposium. 2000 Proceedings. International Symposium on Product Quality and Integrity (Cat. No.00CH37055)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133395423","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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