2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)最新文献

{"title":"Modeling Effect of Underfill Property Evolution on the FCBGA Reliability at Sustained Automotive Underhood Temperatures","authors":"P. Lall, Madhu L. Kasturi, Haotian Wu, J. Suhling, Edward Davis","doi":"10.1109/iTherm54085.2022.9899528","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899528","url":null,"abstract":"The operating conditions inside the automotive underhood involve the sustained exposure of electronics to temperatures in the range of 150 to 200 ℃ for prolonged periods of time. The CTE (coefficient of thermal expansion) mismatch between the chip and the substrate causes assembly-warpage when operating at very high temperatures in flip chip packages. The underfills are used to support the solder balls, which reduces the solder joint strains and improves the fatigue life of the joints. In this paper, the effect of evolution of non-linear viscoelastic properties of two underfills were studied on plastic-work in the solder balls and other lidded FCBGA (Flip Chip Ball Grid Array) package components. To obtain the viscoelastic behavior of underfills, TTS (time-temperature superposition) experiments are performed at 7 discrete frequencies 0.1, 0.21, 0.46, 1, 2.15, 4.64, and 10 Hz in frequency sweep three-point bend mode in DMA. The shift factors are calculated from WLF (Williams-Landel-Ferry) equation as a function of temperature. Using the shift factors, TTS results, and at selected reference temperatures, the Master curves are obtained for storage moduli, loss moduli and tan-delta as a function of frequency. The relaxation modulus, thus bulk and shear modulus, are calculated in time domain using Schwarzl and Struik equation from storage and loss modulus master curves. The bulk and shear modulus curves are fitted with Prony series in ANSYS and Prony series coefficients are implemented in underfill properties. By taking the advantage of symmetry, quarter lidded FCBGA model was built, and two complete thermal cycles were applied from -40℃ to 125℃ to get a steady hysteresis loop. Aging samples include the pristine samples and the sampled aged for 30, 60, and 120 days.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123917341","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":"Thermal-Aware Optimization of SoC Floorplan with Heterogenous Multi-Cores","authors":"J. Yoo, Taekeun An, Chi-young Oh, Youngsang Cho, Heeseok Lee, Yunhyeok Im, Minkyu Kim, Minsu Kim","doi":"10.1109/iTherm54085.2022.9899498","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899498","url":null,"abstract":"As the performance required by System on Chip (SoC) IPs has increased, power consumption and power density have been increased. Since the SoC temperature is increasing, thermal-aware design in SoC, package, and system must meet the required target performance and reliability. Thermal-aware floorplan is an important aspect because self-heating and thermal coupling differ depending on the absolute and relative location of each IP. Moreover, it can be considered highly effective as it costs less than package and system solutions. In this paper, we demonstrate a thermal-aware floorplan optimization method considering the physical design elements of multi-core design in SoC. It also describes a method to reduce the SoC temperature comprehensively. In multi-cores, heating modules (HotSpot Area) must be separated from each other due to mutual thermal coupling. It is comfirmed by thermal simulation that the thermal resistance is much lower than that of all the attached heating modules. Also, Temperature can be reduced at the early design stage by placing the IPs appropriately in the available region across the SoC based on Cooling Zone (CZ), Keep Out Zone (KOZ), and Acceptable Zone (AZ). Simulation results indicates that the effect of thermal-aware floorplan is dominant when compared to package and system.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124086644","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 R-1233zd and HFE-7000 Condenser Performance in Pumped Two-Phase Cooling Systems","authors":"A. Pegallapati, N. Karwa","doi":"10.1109/iTherm54085.2022.9899594","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899594","url":null,"abstract":"The increasing heat flux from chips and high server- and rack-level heat densities in high-performance computing infrastructure have resulted in an increased interest in pumped two-phase cooling. It has been demonstrated that pumped two-phase cooling using dielectric fluorinated fluids in cold plates significantly reduces case temperature and improves case temperature uniformity over single-phase water cooling. Karwa and Yana Motta [1] compared the performance of low-pressure dielectric heat transfer fluids with system pressure less than 60 psi in microchannel cold plates and showed that R-1233zd(E) (normal boiling point: 18.26 °C) provided improved performance over HFE-7000 (normal boiling point: 34.2 °C). The present study extends their work and presents results of experimental and theoretical evaluation of condenser performance in pumped two-phase cooling systems. Tube-fin type air-cooled condensers were simulated using a detailed tube-by-tube model in Genesym™, and the performance of brazed plate water-cooled condensers was determined experimentally. The performance of air-cooled and water-cooled condensers for low-pressure heat transfer fluids R-1233zd(E) and HFE-7000 were compared. It is demonstrated that, for the same performance, R-1233zd(E) requires almost 35% smaller air-cooled condenser as compared to HFE-7000 and the fluid charge in the system can be reduced by 65%. It has been shown that dielectric fluid side heat transfer coefficient is the controlling heat transfer coefficient in brazed plate water-cooled condenser, and up to 20% higher dielectric fluid heat transfer coefficient was achieved for R-1233zd than HFE-7000 in brazed plate condensers. This study shows that R-1233zd(E) is a feasible low-pressure heat transfer fluid option for both air- and water-cooled pumped two-phase cooling systems.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121155002","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":"Design of a Microchannel Heat Exchanger for Extreme Environments (MHXEE)","authors":"Zhengda Yao, R. Mandel, A. Shooshtari, Hugh Alan Bruck, M. Ohadi","doi":"10.1109/iTherm54085.2022.9899621","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899621","url":null,"abstract":"The development of low-cost, high-performance, and compact heat exchangers for extreme environmental conditions will benefit multiple sectors, especially applications in power electronics and aerospace. These heat exchangers enable efficient thermal exchange systems with strict size, weight, and power consumption (SWaP) requirements. In this study, a counter-flow heat exchanger was designed using microchannels to achieve a high-power density (31.1 kW/kg and 195 kW/L) and is capable of operating in high-temperature (800 °C) and high-pressure (80 bar) environments. Two critical aspects of this microchannel heat exchanger for extreme environments (MHXEE) are included: (1) creep resistance associated with operating at high temperatures and (2) pressure drop associated with the microchannels. CFD and stress analyses were conducted to characterize the heat exchanger's thermohydraulic and mechanical performances. By adding internal ribs inside the manifold area, the heat exchange strength was improved at its design condition while the pressure drops remained at acceptable levels. In order to improve this design further, a topology optimization approach was developed using a 2D model, where different optimal material distributions could be determined that focused on optimizing either: (1) the uniformity of the velocity field or (2) the uniformity of the heat flux. This study demonstrated the potential for further using a robust and reliable yet simple topology optimization approach to improve the thermal and mechanical performance of the MHXEE.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"163 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122923967","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":"Pool Boiling Performance of Surfaces Produced by Femtosecond Laser Surface Processing and Copper Hydroxide Nanoneedle Growth","authors":"Justin Costa-Greger, G. Damoulakis, Graham Kaufman, S. Sarin, Chase Pettit, J. Shield, C. Megaridis, C. Zuhlke, G. Gogos","doi":"10.1109/iTherm54085.2022.9899497","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899497","url":null,"abstract":"Copper hybrid functionalization that leads to copper hydroxide nanoneedles grown on top of femtosecond laser surface processed (FLSP) copper microstructures is experimentally studied in saturated pool boiling of distilled water at atmospheric pressure. FLSP was used to fabricate self-organized, hierarchical structures that lead to an inherently superhydrophilic surface. The hybrid scheme involved synthesizing copper hydroxide nanoneedles atop the FLSP microstructures using a dilute solution of sodium hydroxide and ammonium persulfate. The nanoneedles lead to increased surface area and altered cavity dimensions available for nucleation. In addition, a citric acid cleaning process was implemented to remove oxides from the FLSP surface before growing the nanoneedles. The FLSP surfaces with and without citric acid cleaning were tested up to critical heat flux to serve as baselines for comparisons with the hybrid functionalization scheme. Pool boiling results using the hybrid functionalization scheme revealed degraded performance for surfaces which incorporated copper hydroxide nanoneedles due to the increased volume of oxides present from the transition of copper hydroxide to copper oxide during heating. Scanning electron microscope images acquired after boiling tests revealed complete removal of the nanoneedles during testing, illustrating the nanoneedles’ lack of durability under aggressive boiling conditions. The best performance was shown for a sample functionalized using FLSP only and without incorporating citric acid etching or nanoneedle growth. This surface achieved a 22% increase in the heat transfer coefficient compared to the polished surface at a heat flux of approximately 95 W/cm2, albeit at a reduced critical heat flux. Additionally, large degrees of pool boiling inversion were observed for surfaces which did not include the citric acid cleaning process. This observation points to a connection between the oxides produced from the FLSP process and boiling inversion for copper, suggesting that the presence of oxides and associated microstructures are responsible for boiling inversion on high thermal conductivity metals.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"140 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122397851","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 Analysis of a Dual-Evaporator Thermosyphon Cooling System for CPUs and GPUs","authors":"Filippo Cataldo, Yuri C. Crea, R. L. Amalfi","doi":"10.1109/iTherm54085.2022.9899537","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899537","url":null,"abstract":"Thermosyphon cooling systems have great potential to be widely adopted for electronics cooling applications. They combine highly effective heat transfer with passive circulation triggered by the density difference between the liquid and vapour phases. It is not uncommon to have several processing units on a single motherboard, such as the Central Processing Units (CPUs) and Graphics Processing Units (GPUs) in electronic devices, such us desktop computers, servers, telecommunications equipment, etc. Thus, designing a thermosyphon cooling system with multiple evaporators and a single condenser is critical for practical implementations and broad market adoption. In this study, a thermosyphon-based system composed of two evaporators and a single air-cooled condenser is designed and tested for the layout of a desktop computer, removing heat from a CPU and a GPU. Specifically, the vertical CPU evaporator occupies the highest position, while the GPU evaporator is horizontal and located at the bottom of the loop. Both evaporators are in a parallel scheme in the proposed thermosyphon design. The total power dissipation of the thermosyphon-based system is 650 W and is split nonuniformly between the two evaporators (CPU power of 350 W and GPU power of 300 W). The results show that the thermosyphon can effectively cool both processing units without instabilities, with an overall thermal resistance varying between 0.055 and 0.061 K/W in steady-state operating conditions. Overall, the results demonstrate a thermosyphon system’s feasibility, reliability, and high efficiency in a dual-evaporator configuration as a starting point for future and more complex hardware arrangements.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127535007","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":"Prediction of Electrical Performance and Print Geometry for Inkjet Additive Circuits via Statistical Modeling","authors":"P. Lall, Kartik Goyal, Scott Miller","doi":"10.1109/iTherm54085.2022.9899501","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899501","url":null,"abstract":"In this paper, statistical models are developed for the prediction of Inkjet printed structures in regards to their physical and electrical characteristics. Additive printed electronics are constantly evolving and improving by the way they are manufactured. Immense interest is shown due to number of reasons, including the reduced time to manufacture from design stage and the possibilities in the fabrication of various electronic circuits. Different techniques have recently been explored that are extremely cost-effective and can use different types of materials and substrates. Among those, Inkjet, which has been established as a reliable technique in office environment setting, recently started gaining attraction in printed electronics for rapid prototype development. The technique can easily be integrated in current additive manufacturing processes for mass-scale up and roll-to-roll process. However, to deposit functional materials such as metal Nanoparticle inks, Inkjet requires control of certain parameters for fine droplet ejection, thus resulting in fine print structures. With the development of several metal functional inks, it results in time-consuming process that is crucial to avoid in a manufacturing facility. Most commonly used inks that are utilized via Inkjet appears to be either Silver or Copper with Nanoparticle formulations, but recent developments have shown promising interest in particle-free formulations of ink, with low processing temperatures and that can help avoid blockage of Inkjet nozzles. This paper introduces Inkjet technology with various inks and their process-property relationships against their post-print parameters. A design-of-experiments (DOE) matrix is developed for the print parameters space for help in prediction of certain physical and electrical characteristics before starting the print process. The authors’ final aim is to have statistical models that can be used to achieve the desired print width and desired electrical properties.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126547744","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":"Design and Development of an Automated Lithium-Ion Battery Temperature and Internal Pressure Monitoring Device","authors":"Samba Gaye, Jane Catuche, M. Kabir, Jiajun Xu","doi":"10.1109/iTherm54085.2022.9899518","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899518","url":null,"abstract":"Commercial Lithium-Ion batteries (LIBs) are an emerging source of power and energy used in many of emerging applications such as electric vehicles, aircraft backup power, and renewable energy. However, they have short life cycles and will degrade with use and time. LIB aging, which contains different failure mechanisms, is a complicated interrelated process of mechanical and chemical degradations, leading to the formation of solid electrolyte interface (SEI) layer on the electrodes. Numerous experiments have investigated the effects of LIB degradation using Electrochemical Impedance Spectroscopy (EIS); a method used to inspect the impedance of an electrochemical system over a range of frequencies. EIS measurements, coupled with other more conventional methods, can evaluate changes in internal resistance, conductance, capacity, potential, self-discharge, charge acceptance, and cumulative charge/discharge cycles. However, these methods still do not provide a full understanding of LIB aging. Hence, complementary strategies are needed to help achieve better results and predictability during high-rate cycling. To offer as an alternative method, a few studies have focused on the internal gas evolution along with operating temperatures of Li-ion cells to be directly linked to the aging/failure mechanisms of LIBs. This was accomplished by designing a custom gas test chamber that allowed monitoring and measure both internal pressure and temperature of a LIB while being cycled. In the present study, an improved design of the existing gas test chamber was proposed and tested. The proposed design is able to achieve the following: 1) improved puncturing mechanism using automation, 2) improved pressure monitoring system by minimizing the free volume, 3) minimized the heat transfer away from the cell using better insulation, 4) improved temperature monitoring system by adding the use of pyrometers (infrared thermometer) to measure the temperature along with the thermocouples.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126730634","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":"Numerical evaluation of bimetallic self-adaptive fins acting as flow disturbing elements inside a microchannel","authors":"M. Vilarrubí, Desideri Regany, Francesc X. Majós, M. Ibañez, J. Rosell, J. Illa, F. Badia, A. Amnache, Éttienne Léveillé, R. Pandiyan, L. Fréchette, J. Barrau","doi":"10.1109/iTherm54085.2022.9899648","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899648","url":null,"abstract":"The continuous increase in power density of integrated circuits (IC) due to the ever-increasing rate of data and communications and the constant push for size and costs reduction, is settling thermal management as one of the major concerns for the ICT industry. Current cooling solutions focus on high compactness and low thermal resistance. Nevertheless, several electronic applications, such as multicore processors or 3D-IC, present non-uniform and time-dependent heat load scenarios, what leads current systems to both oversized pumping powers for changing conditions and optimized temperature uniformities of the chip only for a given heat load distribution. To overcome these problems, this work proposes a system based on self-adaptive fins acting as passive thermal actuators, where the fins will be activated, without any external excitation, in function of their own temperature due to the principle of thermal expansion of the materials. The self-adaptive fins are based on bimetals that act as flow disturbing elements inside microchannels only for high cooling demands, otherwise, the fins remain in a flat position to reduce the pressure drop of the cooling device. Consequently, the system is able to tailor its internal geometry to time dependent and non-uniform heat flux distributions, optimizing the local heat transfer enhancement and the pressure drop to the instantaneous cooling needs. The impact of this cooling solution within a microchannel has been numerically evaluated in this work, as well as different structural parameters of the bimetallic fins to ensure the self-adaptive behavior. Results showed a 40% heat transfer enhancement and a pumping power reduction up to 34% compared with a system of fixed vortex generators.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114106885","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":"Assembly Reliability of eWLP, Die- and Die-Size BGA","authors":"R. Ghaffarian","doi":"10.1109/iTherm54085.2022.9899504","DOIUrl":"https://doi.org/10.1109/iTherm54085.2022.9899504","url":null,"abstract":"This paper presents assembly challenges as well as solder joint thermal-cycle reliability of mixed area array packaging and flip-chip die technologies. These were: (1) eWLP-LGA, 196 land patterns, 0.4mm pitch, (2) Cu-FC (CC80), flip-chip die with copper pillar, 1048 bumps, and (3) CVBGA, 360 balls, 0.4mm pitch and with either lead-free or tin-lead solder balls.Twenty-seven (27) PCBs were assembled with a number of variables and rejected assemblies. Acceptable assemblies with and without underfill were subjected to thermal cycling between –40°C and 125°C for solder-joint reliability characterization and failure-mechanism assessments. The 2-parameter Weibull plots delineated cumulative failures and optical X-sectional characterization presented failure mechanisms and locations.","PeriodicalId":351706,"journal":{"name":"2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm)","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116918238","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}