Volume 7: Operations, Applications, and Components最新文献

{"title":"Managing Pressure Equipment Aging in Plants With Major Accident Hazard: A Methodology Satisfying the Requirements of the European Directive 2012/18/UE Seveso III","authors":"P. Bragatto, C. Site, M. Milazzo, A. Pirone, M. R. Vallerotonda","doi":"10.1115/PVP2018-84687","DOIUrl":"https://doi.org/10.1115/PVP2018-84687","url":null,"abstract":"Attention to be paid to the aging of industrial facilities has been growing in the last ten years, both by public authorities and industrial executives. Many process plants, operating in Europe, have reached or exceeded their project nominal life and the safe management of aging is an urgent question. Failures, due to aged chemical process plants, cause the release of hazardous materials with severe consequences for people and workers. To counteract this phenomenon, plant operators carry out many technical activities, including non-destructive controls on piping and vessels, by adopting sophisticated methods (e.g. Risk Based Inspection RBI).\u0000 The European Directive 2012/18/UE (Seveso III) for the control of Major Accident Hazard (MAH) introduced a few requirements for the safe aging of critical equipment, which must be verified during mandatory audits. The aim of this work is to present a synthetic methodology that can be useful for both Seveso auditors and industrial managers for evaluating the adequacy of the measures to control the aging of critical equipment.\u0000 To achieve a synthetic assessment of the adequacy of the aging management programs, a compensated index method has been developed, which is a simple and easy-to-use tool. The use of an index method inevitably introduces a degree of uncertainty. However, if it is compared to other qualitative methods, such a tool offers the advantage of a major clarity in the assessment process. This paper discusses a practical application of the method within inspection programs, as required by the art. 27 of Seveso III Directive.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125952836","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}

{"title":"Financial Optimization of a Preventive Replacement Strategy for Individual Components","authors":"J. Cluever, T. Esselman, S. Harvey","doi":"10.1115/PVP2018-84833","DOIUrl":"https://doi.org/10.1115/PVP2018-84833","url":null,"abstract":"Électricité de France (EDF) has developed the Investment Portfolio Optimal Planning (IPOP) software tool [1] to be released with the Integrated Life Cycle Management (ILCM) software tool developed by the Electric Power Research Institute (EPRI) [2]. IPOP is an extremely powerful tool that uses genetic algorithms to provide an optimal strategy for investment in spare components and preventive replacements of multiple components at multiple power plant stations across an entire fleet. A drawback of IPOP is that it requires an extensive amount of user information to run even a single component. In response, Component Optimization Analysis Tools (COATs) was developed to simplify the process of deriving an optimal strategy for purchasing spares and replacements for a single component. This paper describes a two-layer algorithm used in the replacement strategy optimization in COATs. The inner layer consists of a Monte Carlo simulation that estimates the Expected Net Present Value (ENPV) of a given replacement strategy. A strategy consists of: the age of a component at which it needs to be replaced, the age of a component at which a spare should be purchased, years left in the plant at which to skip a scheduled replacement, and the end of life at which the scheduled replacement is skipped; and the years left in the plant at which no more spares are purchased. The Monte Carlo analysis uses these four strategy inputs with component costs, acquisition times, and reliability curves with plant downtime costs to calculate an ENPV for that strategy. The outer layer of the algorithm is an optimization layer that can use either Bayesian optimization or genetic algorithms to maximize the ENPV. These optimization algorithms are routinely available in various software packages and effectively treat the ENPV Monte Carlo as a black box function. An efficiency comparison is given between the two optimization algorithms to demonstrate under which conditions each algorithm out performs the other.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125174212","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}

{"title":"Comparison of Thermal Test Using Slice Model and Half-Scale Model of Shipping Package","authors":"K. Bang, Seung-Hwan Yu, Ju-chan Lee, W. Choi","doi":"10.1115/PVP2018-84260","DOIUrl":"https://doi.org/10.1115/PVP2018-84260","url":null,"abstract":"KORAD-B/II shipping packages are used to transport C4 concrete packages that are temporarily stored at the HANUL nuclear power plant. These packages must therefore satisfy the requirements prescribed in the Korea Nuclear Safety Security Commission Act 2014-50, the IAEA Safety Standards No. SSR-6, and US 10 CFR Part 71. These regulatory guidelines classify a KORAD-B/II shipping package as a Type B package, and state that this type of package must be able to withstand a temperature of 800 °C for a period of 30 min. It is desirable to conduct a test using a full-scale model of a shipping package when performing tests to evaluate its integrity. However, it is costly to perform a test using a full-scale model. Therefore, to evaluate the thermal integrity of a KORAD-B/II shipping package, thermal tests were conducted using a slice model. For comparison purposes, a thermal test was also carried out using a half-scale model. In the first thermal test using a slice model, the maximum surface temperature of the cask body was higher than the permitted maximum temperature limits owing to incomplete combustion. In the second thermal test using a slice model and in the thermal test using a half-scale model, the maximum temperature of the cask body was lower than the permitted maximum temperature limit. Therefore, the thermal integrity of the KORAD-B/II shipping package could be considered to be maintained. The temperature results from the thermal test using a slice model were higher than those of the thermal test using a half-scale model. Therefore, the effect of flame on a single-layer shipping package without neutron shielding, such as the KORAD-B/II shipping package, seems to be affected by the reduction in the time rather than the size reduction.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127829859","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}

{"title":"Experimental Research on the Effect of Heating Temperature, Demulsifier Dose and Water Cut on the Oil-Water Separation in Three-Phase Separator","authors":"Ang Li, Jian-Jie Bai, Yun Shen, Han Jin, Wen Wang, J. Gong, Yaorong Feng","doi":"10.1115/PVP2018-84285","DOIUrl":"https://doi.org/10.1115/PVP2018-84285","url":null,"abstract":"The three-phase separator has a wide range of applications in oil production industry. For the purpose of studying the effect of heating temperature, demulsifiers and water content on the separation of oil-water mixture in the three-phase separator, eight kinds of oil samples were taken from different oil transfer stations in Changqing Oilfield and the mixtures were prepared by stirring method. To simulate the two-stage dehydration process, the first stage dehydration experiments without any heating were performed on mixtures at the dose of 100ppm demulsifer at 20°C, and the water cut of these mixtures is the same as that of the gathering pipeline in each oil transfer station. The water cut of the upper crude oil was measured after 40 minutes, and the values of them ranged from 0.5 vol% to 65.2 vol%. No visual stratification was observed for the sample most difficult to separate, so it was selected to conduct the second stage dewatering process. Three bottles of the same mixture were prepared and heated to 30°C, 40°C and 50°C, respectively. The results showed that all of them stratified in 10 minutes, and the water-cut values of the upper oil layer were 1.4 vol%, 0.5 vol% and 0.3 vol%, respectively, compared to 65.2 vol% at 20°C. When the concentration of demulsifier was changed to 200ppm and 300ppm, the results exhibited almost no differences. So it is deduced that the further improvement of heating temperature and demulsifier dose have limited enhancement on oil-water separation. At Last, 35 vol%, 50 vol%, 70 vol% and 85 vol% water cut mixtures of the special oil sample were made to experiment as previously. In consequence, the 35 vol% water-cut emulsions presented a relatively slow rate of oil-water stratification at low heating temperature, and the oil content of the lower separated water was improved by the addition of demulsifier dosage above 100ppm when the water cut was 90 vol%. It is indicated that high heating temperature is necessarry for low water-cut mixtures oil-water separation and can be appropriately reduced to save energy consumption as the water cut continues to rise. The demulsifier dosage is also neccessary be controlled in high water cut period. These experimental data provide the basis for the further optimization operation of the three-phase separator.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127940009","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}

{"title":"Long-Term Performance of Elastomer Seals: From Aging Tests to Lifetime Estimations","authors":"M. Jaunich, A. Kömmling, J. Horn, H. Völzke, D. Wolff","doi":"10.1115/PVP2018-84631","DOIUrl":"https://doi.org/10.1115/PVP2018-84631","url":null,"abstract":"Elastomers show a high versatility which makes them ideal materials for sealing applications in various fields. Especially under changing application conditions the high recovery potential of this class of material is beneficial to compensate temperature or pressure fluctuation, and geometrical changes resulting from mechanical loads in e.g. accident conditions. Out of these reasons elastomers are also used in containers for low and intermediate level radioactive waste and for spent fuel transportation casks. In casks designed for low and intermediate level waste elastomer seals can act as primary seal responsible for the containment function whereas in spent fuel storage and transportation casks (dual purpose casks (DPC)) elastomer seals are used as auxiliary seals to allow leakage rate measurements of metal barrier seals. An inherent prerequisite for this kind of application is the long time-scale of operation without or with limited possibility of seal replacement. In Germany an interim storage license for DPC’s is typically issued for 40 years, a timeframe which might increase in the future due to challenges of the final repository siting procedure. For low and intermediate level waste, also long time periods are required before final disposal can be achieved. Therefore, the performance of elastomer seals over extended time periods is, as for other applications, of high importance.\u0000 A typical approach to ensure long-term functionality is to perform accelerated aging tests to calculate an estimated lifetime by assuming e.g. Arrhenius like equations for the timetemperature relationship. This approach requires a suitable end of life criterion considering the application of interest. This often can represent a challenge on its own.\u0000 As BAM is involved in most of the cask licensing procedures and especially responsible for the evaluation of cask-related long-term safety issues we initiated several test programs for investigating the behavior of elastomer seals. Experiments concerning the low temperature performance down to −40 °C and the influence of gamma irradiation have been started first. Currently the thermal aging behavior of elastomer seals, which is the topic of this contribution, is examined.\u0000 For our aging investigations we use a broad approach to first determine the property changes in different elastomer materials due to thermo-oxidative aging at elevated temperatures and secondly, we test how the typical methods of lifetime extrapolation can be applied to these results. This approach enables us to detect and exclude undesired side effects which very often influence lifetime estimations. In this contribution, our recent results are extended. The results show that lifetime estimation based on single material properties can be misleading and therefore a combination of several methods is recommended.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123400500","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}

{"title":"Temperature Prediction of a TN-32 Used Nuclear Fuel Canister Subjected to Vacuum Drying Conditions","authors":"M. Higley, M. Hadj-Nacer, M. Greiner","doi":"10.1115/PVP2018-84844","DOIUrl":"https://doi.org/10.1115/PVP2018-84844","url":null,"abstract":"In this work, a geometrically-accurate two-dimensional (2D) computational fluid dynamic (CFD) model of a used nuclear fuel cask, that can contain up to 32 pressurized water reactor (PWR) used nuclear fuel (UNF) assemblies, is constructed. This model is similar to the TN-32 cask employed in the ongoing high-burnup (HBU) Spent Fuel Data Project lead by the Electric Power Research Institute (EPRI). This model is used to predict the peak cladding temperature under vacuum drying conditions. Due to the symmetry of the cask, only one-eighth of the cross-section is modeled. Steady-state simulations that include the temperature-jump boundary conditions at the gas-solid interfaces are performed for different heat generation rates in the fuel regions and a range of dry helium pressures, from ∼105 to 100 Pa. These simulations include conduction within solid-gas regions and surface-to-surface radiation across all gas regions. The peak cladding temperatures are reported for various heat generation rates and rarefaction conditions, along with the maximum allowable heat generation that brings the cladding temperatures to the radial hydride formation limit. The results showed that the decrease of helium pressure significantly increased the temperature of the cladding material compared to the atmospheric pressure condition.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115117758","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}

{"title":"A Case Study: Balanced Globe Valves Failure, Root Cause, and Recovery","authors":"Ronald S. Farrell, M. Laney, Preston A. Vock, Andrew Garcia","doi":"10.1115/PVP2018-84757","DOIUrl":"https://doi.org/10.1115/PVP2018-84757","url":null,"abstract":"During the pre-operational blowdown testing of the AP1000® Automatic Depressurization System (ADS), it was observed that several ADS Stage 1-3 balanced globe valves did not fully open; however, the valves did sufficiently open to provide adequate ADS flow to meet the ADS System depressurization safety function. Since the Main Control Room did not receive a full-open signal indicating that the ADS valves fully completed the valve stroke, the valves were disassembled to determine the potential cause and scoring was observed on the valve disk and valve body guide surfaces. A technical design review team was formed and determined that the primary cause was unequal thermal expansion between the thin walled valve disk and the thicker valve body resulting in interference during valve stroking. Classical thermal and CFD analyses were used to confirm that, once a normally closed globe valve received its signal to open, there was not sufficient “soak time” for the thicker valve body to reach thermal equilibrium with the thinner valve disk; thus, as the valve disk stroked open as it moved along the guide surfaces, there was not sufficient clearance resulting in scoring between the disk and the guides preventing the disk from stroking fully open. The solution was to maximize the clearance between the disk and body guides to allow for thermal growth during the ADS blowdown event. However, changing the clearances between the body guides and disk may compensate for thermal growth but may also impact the valve’s “balancing” function; therefore. disk piston rings were added to restore the tight clearance needed for “balancing” yet sufficiently provide relief from the effects of thermal growth. A prototype valve was retrofitted, and small scale validation tests were performed using air to challenge the changes. The preliminary performance test results were utilized by system designers to better understand the valve function in the event of an ADS blowdown. Although no full-scale retrofit testing was practical using high temperature saturated steam, as no suitable test facility was available within the plant operational test schedule time frame, the quality of the recovery effort yielded a high degree of confidence that the system retest would be successful. The project came to a successful conclusion upon two successful operational ADS blowdown tests with the retrofits installed.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"505 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116194943","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}

{"title":"New Generation of Monitoring Systems: From Measurement to Numerical Simulation","authors":"B. Jouan, B. Heinz, Oana-Zenaida Pascan","doi":"10.1115/PVP2018-84598","DOIUrl":"https://doi.org/10.1115/PVP2018-84598","url":null,"abstract":"This paper presents a new method for monitoring systems with direct coupling of measurement data and a finite element model of a mechanical component. In the presented first case study the measurement data received from a monitoring system is coupled with a finite element model developed in Code_Aster, showing the possibility of minimizing the efforts of data-model coupling on complex components.\u0000 A thermo-mechanical calculation of a generic regenerative heat exchanger of a nuclear power plant will be used as an example to describe the opportunities and the limitations of the use of numerical simulation in modern monitoring systems. The experimental measurements and the thermo-mechanical numerical simulation process will be presented. The projection hypothesis that allows the transition from locally measured temperature to the numerical model will be described. The relation between computing time, sampling rate of the data acquisition system and refinement of the numerical mesh will be analyzed and discussed in terms of computation perspective.\u0000 The paper explains how the measurement data can be projected on the mesh of a mechanical component with Code_Aster and how the numerical simulation can be fed on the measurement data. In an outlook, the use of this method in future monitoring systems will be discussed under consideration of real world problems and applications in nuclear power stations.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114809220","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}

{"title":"Experimental Investigations of the Burning Behaviour of Transport Package Impact Limiters and of Fire Spread Impact Onto the Cask","authors":"Marina Erenberg, Claus Bletzer, Martin Feldkamp, A. Musolff, M. Nehrig, F. Wille","doi":"10.1115/PVP2018-84714","DOIUrl":"https://doi.org/10.1115/PVP2018-84714","url":null,"abstract":"Accident safe packages for the transport of spent nuclear fuel and high-level waste shall fulfil international IAEA safety requirements. Compliance is shown by consecutive mechanical and thermal testing. Additional numerical analysis are usually part of the safety evaluation. For damage protection some package designs are equipped with wood filled impact limiters encapsulated by steel sheets. The safety of these packages is established in compliance with IAEA regulations. Cumulative mechanical and fire tests are conducted to achieve safety standards and to prevent loss of containment. Mechanical reliability is proven by drop tests. Drop testing might cause significant damage of the impact limiter steel sheets and might enable sufficient oxygen supply to the impact limiter during the fire test to ignite the wood filling. The boundary conditions of the fire test are precisely described in the IAEA regulatory. During the test the impact limiter will be subjected to a 30 minute enduring fire phase. Subsequent to the fire phase any burning of the specimen has to extinguish naturally and no artificial cooling is allowed. At BAM a large-scale fire test with a real size impact limiter and a wood volume of about 3m3 was conducted to investigate the burning behaviour of wood filled impact limiters in steel sheet encapsulation. The impact limiter was equipped with extensive temperature monitoring equipment. Until today burning of such impact limiters is not sufficiently considered in transport package design and more investigation is necessary to explore the consequences of the impacting fire. The objective of the large scale test was to find out whether a self-sustaining smouldering or even a flaming fire inside the impact limiter was initiated and what impact on the cask is resulting. The amount of energy, transferred from the impact limiter into the cask is of particular importance for the safety of heavy weight packages. With the intention of heat flux quantification a new approach was made and a test bench was designed.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114443187","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}

{"title":"Piston-Lift Check Valve Flow Verification Using CFD","authors":"M. Laney, Ronald S. Farrell","doi":"10.1115/PVP2018-84672","DOIUrl":"https://doi.org/10.1115/PVP2018-84672","url":null,"abstract":"Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an extension of paper PVP2017-66269, “Check Valve Flow and Disk Lift Simulation Using CFD” [1], and utilizes some of the same concepts to characterize flow through piston-lift check valves. The previous example considered a swing check valve involving rotational movement; this example considers a vertical lift piston check valve involving translational movement. Specifically, CFD was used to determine valve flow coefficients (CV) as a function of disk lift position as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The CFX application, which is part of the ANSYS suite of finite element software, was used to determine the flow characteristics. As presented in PVP2017-66269, balancing flow-induced forces on the check element and considering the disk assembly weight, the valve lift behavior can be predicted. Results from the CFX analysis were compared to recent test results of a skirted disk-piston check valve and previous test results of a standard disk-piston check valve. The results showed good agreement in most cases. This validates that flow characteristics across valves with different types of check elements at different disk lift positions can be reliably predicted using CFD analysis. It is important to note that while the test results and CFD analysis showed good agreement, it was vital that actual testing be performed in order to validate the approach. This follows the recommendation outlined in the previous paper.","PeriodicalId":339189,"journal":{"name":"Volume 7: Operations, Applications, and Components","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121504518","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}