2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)最新文献

{"title":"Thermal conduction in graphite flake-epoxy composites using infrared microscopy","authors":"Rajath Kantharaj, Ishan Srivastava, Kunal R. Thaker, Aalok U Gaitonde, A. Bruce, J. Howarter, T. Fisher, A. Marconnet","doi":"10.1109/ITHERM.2017.8023960","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.8023960","url":null,"abstract":"Thermally conductive polymer composites, in particular those composed of polymers and carbon-based nanomaterials, are promising for thermal management in electronic devices because they offer high thermal conductivity at low filler loading. The effective thermal properties of these composites exhibit high variability that depend on the topological arrangements and morphological characteristics of the filler particles. In order to tailor the thermal conduction within these composites for use as an efficient heat dissipation material, careful control of the microstructural arrangement of the filler material is required. In this work, we use infrared (IR) microscopy to characterize thermal transport through epoxy composites containing sub-millimeter sized graphitic flakes as filler particles. Graphite flake-epoxy composites of two volume fractions (3%, 25%) are prepared and characterized using an infrared microscope with a temperature resolution of 0.1 K that images the temperature distribution at the top surface of the composite subject to a temperature gradient. The effective thermal conductivity of the composite with a 25% filler fraction was found to be 2.9 W/m-K, a factor of 16 higher than the neat epoxy. With the micron-scale resolution of the IR microscope, the steady-state particle-scale temperature fields within the composite are directly observed and highlight the non-uniform heat transfer pathways. This local temperature analysis reveals the impact of important microstructural features such as clustering of filler particles. Ultimately, this approach could be used to investigate percolation and anisotropic heat conduction in composites with shear aligned particles.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125360814","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":"Characterization of microfluidic operations underlying an electrowetting heat pipe","authors":"R. Hale, V. Bahadur","doi":"10.1109/ITHERM.2017.7992543","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992543","url":null,"abstract":"The heat transport capacity of heat pipes is limited by the capillary pressure generated in the wick that pumps the condensate. The current authors recently proposed a novel heat pipe architecture, in which the wick is replaced by electrowetting (EW)-based pumping in the adiabatic section. An electrowetting heat pipe (EHP) overcomes the capillary limit in heat pipes and can enable compact, ultralow power consumption heat pipes, to transport kiloWatt heat loads over long distances. This work studies the microfluidic operations that are the basis of the EHP. Experiments are conducted to estimate the maximum channel gap which sustains reliable EW pumping. This is an important consideration, since the heat transport capacity scales linearly with the channel gap. Experiments are also conducted to estimate the maximum channel gap at which EW voltages can split droplets. This is important to ensure EHP operability in the event of droplet merging. Experiments are also conducted to demonstrate EW-induced droplet generation from an open-air reservoir. This mimics the interface between the condenser and adiabatic sections. All these experiments are conducted on devices manufactured by a novel and scalable manufacturing technique. The results suggest that planar EHPs (water-based) with a 10 cm by 4 mm cross section can transport 1.6 kW over 1 meter long distances, with a thermal resistance of 0.01 K/W.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126228683","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":"Improved finite element modeling strategies with multipoint constraints for BGA packages subjected to thermal cycling","authors":"Chienchih Chen, J. Suhling, P. Lall","doi":"10.1109/ITHERM.2017.7992651","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992651","url":null,"abstract":"Finite Element simulations are often used to study the reliability of solder joints subjected to thermal cycling. Packaging configurations are becoming more complex to accommodate better functionality and performance. Increased complexity leads to several challenges for FE models including difficulties modeling thin layers and interfaces, as well as keeping the total numbers of nodes and elements to reasonable levels so that computation times can be practical. To reduce the use of high-density meshes and to relax the restrictions of nodal connections, the technique of Multi-Point Constraints (MPC) is often used in finite element analysis. In the MPC method, constraints are enacted between different degrees of freedom of the model to simply transition between finely and coarsely meshed regions. MPC algorithms require additional DOF constraints on a FE model; and extra contact nodes/elements are deployed between the interfaces of contacting elements. MPC methods can be implemented with materials having linear or nonlinear mechanical behavior. The accuracy and efficiency of MPC-based finite element simulations for electronic packages have not been evaluated completely in the literature. In this work, an improved MPC based FE modeling strategy was developed for BGA packages to reduce the total number of elements (including both conventional and MPC elements), and thus reduce the simulation time. In addition, the new method can improve the simulation accuracy relative to models prepared using conventional meshing strategies. The proposed technique allows for different types of mesh patterns (circular pattern from solder joint and rectangular patterns from other component) to be connected in a package assembly while reducing the overall number of elements in the model. The proposed approach works with both symmetric and non-symmetric solder ball arrays, and achieves a good balance between simulation cost and simulation accuracy.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126329835","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":"Effect of subcooling, flow rate and surface characteristics on flow boiling performance of high performance liquid cooled immersion server model","authors":"S. Chandrasekaran, J. Gess, S. Bhavnani","doi":"10.1109/ITHERM.2017.7992582","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992582","url":null,"abstract":"The dramatic increase in data center power consumption due to amplified global data traffic, combined with the demand for compact and energy-efficient data centers, have resulted in liquid immersion cooling gaining a prime focus as a thermal management strategy. As the technology finds its way to commercial applications, extensive knowledge on the effect of critical operational and system parameters on thermal performance is more essential than ever. The experimental study discussed in this paper addresses this by investigating the effect of subcooling, mass flow rate and surface enhancement on the flow boiling performance of a small form factor cooling system with vertically-oriented array of heaters that simulate electronic chips on a printed circuit board. Heat flux values up to 20.5 W/cm2 were achieved with a bare silicon surface for the highest subcooling and flow rate used in this study. Experiments were also conducted on two surface enhancements attached to the bare die — a sintered copper microporous heat sink and a heat sink with an array of microscale fins. With microfinned surface heat flux values up to 20.8 W/cm2 were achieved at surface temperatures less than 70°C. For the microporous surface, even higher heat flux values were achieved with increase in subcooling and flow rate.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121420511","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 first-principles study of phonon transport properties of monolayer MoSe2","authors":"Zhequan Yan, M. Yoon, Satish Kumar","doi":"10.1109/ITHERM.2017.7992464","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992464","url":null,"abstract":"MoSe2 as one of the promising two-dimensional transition metal dichalcogenides (TMDCs) recently emerged as promising alternative of graphene for nano-electronic and opto-electronic devices. However, the heat removal is a critical issue for devices using two-dimensional (2D) materials, and low thermal conductivity of monolayer MoSe2 can significantly affect the performance and reliability of electronic devices. In this study, we use the density functional theory (DFT) and the phonon Boltzmann transport equation (BTE) to study the phonon transport properties of monolayer MoSe2 and compared the results with MoS2. The iterative solution of the BTE is used to predict the thermal conductivity of MoSe2, which is compared with the relaxation time approximation. Model for considering effect of sample size and defects are developed for monolayer MoSe2. Our results show the impact of sample size, Se vacancies, boundary and anharmonic phonon scattering on the thermal conductivity of MoSe2. Defect model is built based on the phonon scattering caused by the missing atom mass and the change of force constants between the under-coordinated atoms near the vacancies. Results indicate that the presence of 1%, 2% and 4% Se vacancies decrease the thermal conductivity of monolayer MoSe2 by 11.2%, 23.4% and 46.2% at room temperature. The results from this work will help in understanding the mechanism of phonon transport in 2D materials and provide insights for the future design of MoSe2-based electronics.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126777636","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":"Flow optimizer architecture designs in high powered computing coolant chambers","authors":"P. Subrahmanyam, Y. Pang, Amy Xia, T. Chao, R. Sahan, Muhammad Ahmad, R. Mohammed","doi":"10.1109/ITHERM.2017.7992538","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992538","url":null,"abstract":"With the ever increasing trend of cramming more transistors on the silicon and the consequential increase in the thermal design power, combined with stacked die and multiple die configurations inside the package footprint, optimized coolant chambers becomes an imperative design need to remove heat efficiently from the silicon. Liquid cooling is investigated to efficiently meet the challenges of high heat loads on several different fin geometries, lowering thermal resistance, and lower noise. Branching flow evenly inside the coolant chamber is vital for optimal performance of the chamber. In this paper, we present computational investigations for improving the thermal performance of a liquid-cooled chamber by optimizing the coolant flow inside the chamber with the aid of novel symmetric baffles strategically located at the inlet and outlet. Flow animation visualization from CFD simulations also show that the baffle introduces turbulence inside the liquid-cooled chamber eliminating stagnant zones especially in the corners. A numerical conjugate convection in the channel and conduction on the fin plate/substrate heat transfer model was developed and setup to run for seven different fin geometries using Ansys Icepak CFD solver. A k-ε model was used to predict the turbulent flow and heat transfer through all the different finned coolant chamber. A new type of miniaturized fin, based on the NACA-0020 airfoil is introduced as a staggered array of pin fin configuration inside liquid cooled chambers and computationally investigated at several inlet velocities ranging from 0.5 m/s to 3.0 m/s (2000 ≤ Re ≤ 12,000) characterizing the variation of surface Nusselt number with Reynolds number. Surface Nusselt number, a dimensionless heat transfer coefficient is investigated along the surfaces of all the fins to predict the convective cooling capability of the fins being considered. Simulation results reveal that NACA-0020 airfoil fin structure with a 0.23 airfoil thickness-to chord length ratio, has the best performance compared against all the other fins investigated in this study. The findings from this investigation can improve thermal performance of liquid cooled heat sinks across a wide range of package powers.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121109301","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":"Nanomechanical characterization of IMCs formed in SAC solder joints subjected to isothermal aging","authors":"Abdullah Fahim, Sudan Ahmed, J. Suhling, P. Lall","doi":"10.1109/ITHERM.2017.7992645","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992645","url":null,"abstract":"Isothermal aging of lead-free Sn-Ag-Cu (SAC) solder joints leads to growth of intermetallic (IMC) particles in the solder bulk as well as growth of intermetallic layers at the joint interfaces with copper bond pads. Fracturing near the interfacial IMC layers is often found to be the primary reason for failures caused by drop impacts. The IMCs in SAC joints are primarily Ag<inf>s</inf>Sn and Cu<inf>6</inf>Sn<inf>5</inf> binary compounds. Cu-Ni-Sn based ternary IMCs can also form at the interface of Ni containing surface finish (i.e. ENIG) and SAC solder. The mechanical properties of these IMCs are very different than those of the Sn rich dendrites and Cu pads. Nanoindentation (NI) techniques are powerful tools to characterize mechanical properties of small particles and thin layers. In this study, the mechanical behaviors of IMC particles and layers in SAC solder joints have been characterized using nanoindentation. SAC bga solder joints were first aged for 6 months at T = 125 °C. Test samples were subsequently prepared by cross-sectioning the aged solder joints, and then molding them in epoxy and polishing them to prepare the joint surfaces for microscopy and nanoindentation. Intermetallics formed in the bulk solder region, copper pad and SAC solder interface, and ENIG plating finish and SAC solder interface were observed and detected using SEM and the energy-dispersive x-ray spectroscopy (EDX) technique. The same intermetallics were then indented to measure their room temperature mechanical properties including the elastic modulus, hardness, and creep strain rate. To ensure the indentation occurred at the desired phase, SPM imaging was done prior and after the indentations. As expected, the measured properties of the IMCs were significantly higher than the Sn-matrix forming the solder joints. The measured elastic modulus and hardness values were 98.1 ± 6.3 and 5.80 ± 0.70 GPa for the Cu<inf>6</inf>Sn<inf>5</inf> layers at the joint and copper bond pad interfaces, 132.5 ± 4.5 and 8.58 ± 1.13 GPa for the Cu<inf>1-x</inf> Ni<inf>x</inf>)<inf>6</inf>Sn<inf>5</inf> layers at the joint and ENIG plating finish interfaces, and 75.2 ± 4.0 and 3.085 ± 0.50 GPa for the AgsSn IMC particles in the solder joint bulk. These are all much higher than the values of 42.7 ± 2.3 and 0.21 ± 0.12 GPa measured for the β-Sn phase in the solder joint bulk. Creep testing performed at 25 °C revealed that the (Cu<inf>1−x</inf>Ni<inf>x</inf>)6Sn<inf>5</inf> IMC layers had the lowest steady state secondary creep rate of 1.088 × 10⁻³ sec⁻¹, whereas the Cu6Sn5 layers had a creep rate of 1.66 × 10⁻³ sec⁻¹, and the Ag<inf>s</inf>Sn IMC particles had a creep rate of 2.34 ×10⁻³ s⁻¹. The creep stress exponents were evaluated from log-log plots of the strain rate vs. applied stress data.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116733002","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":"Two-phase liquid cooling system for electronics, part 1: Pump-driven loop","authors":"T. Salamon, R. L. Amalfi, N. Lamaison, J. Marcinichen, J. Thome","doi":"10.1109/ITHERM.2017.7992551","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992551","url":null,"abstract":"An experimental study to analyse the thermal performance of a two-phase pump-driven loop for electronics cooling is presented, with the target application being a telecommunications equipment shelf having multiple circuit pack cards each dissipating several hundred Watts of power. The upward flow boiling heat transfer and pressure drop of R134a within an evaporator prototype fabricated with 18 individual microcooling zones to cool multiple electronics heat sources was investigated. The electronic heat sources were emulated by multiple copper heater blocks with embedded cartridge heaters, where each heat source was capable of dissipating more than 100 W, for a total power dissipation larger than 1800 W. Experimental results demonstrated the best cooling capability at a mass flow rate of 140 kg/h, uniform heat load of 1800 W to the 18 microcooling zones, system pressure of 600 kPa and inlet subcooling of 2 K in which the temperature difference between the evaporator and coolant inlet was 7.1 K with a uniform flow distribution within the evaporator.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113960662","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":"Two-phase flow regimes in a U-shaped diabatic manifolded-microgap channel","authors":"D. Deisenroth, M. Ohadi, A. Bar-Cohen","doi":"10.1109/ITHERM.2017.7992474","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992474","url":null,"abstract":"Embedded cooling — an emerging thermal management paradigm for electronic devices — has motivated further research in compact, high heat flux, cooling solutions. Reliance on phase-change cooling and the associated two-phase flow of dielectric refrigerants allows small fluid flow-rates to absorb large heat loads. Our previous research as well as work of others has shown that dividing chip-scale microchannels into parallel arrays of channels with novel manifold designs can produce very high chip-scale heat transfer coefficients with low pressure drops. In such manifolded microchannel coolers, the coolant typically flows at relatively high velocities through U-shaped microgap channels, producing centripetal acceleration forces on the fluid that can be several orders of magnitude larger than gravity. The impact of such large accelerations on the two-phase flow regimes in microgap channels, and their associated transport rates, are not well understood. Moreover, because the channels are very small and optically inaccessible, the flow regimes occurring in such manifolded microchannels have yet to be imaged and documented. The present effort analyzes the effects of such high centripetal acceleration on two-phase flow characteristics, including flow morphology. Since the available literature deals almost exclusively with macroscale and miniscale channels, the differences between macroscale and microscale two-phase flows are identified and discussed. The paper also shows, using dimensionless numbers to characterize the prevailing two-phase flow regimes, that results of previous U-channel visualizations in miniscale geometries, approximately an order of magnitude larger in every geometrical dimension than the microgap channels of interest, can provide insight into the flow regimes occurring in very high-performance microgap channels.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123793902","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":"Development of algorithms for real-time estimation of smartphone surface temperature using embedded processor","authors":"Masatoshi Ishii, Y. Nakashima","doi":"10.1109/ITHERM.2017.7992609","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992609","url":null,"abstract":"In smartphone and tablet devices, surface temperature management is required to ensure safety for the prevention of burn injuries. Therefore, mobile devices must have a mechanism of functional restriction to control the surface temperature, but this in turn also leads to performance degradation. It is preferable to control the surface temperature under the safety threshold while minimally affecting performance. The surface temperature must therefore be known precisely and in real-time. In this study, algorithms were developed for smartphone surface temperature estimation within 1 °C of the root mean square (RMS) error using internal thermistor sensor data that can be executed on a smartphone's embedded processor using a negligible amount of resources.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"2 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113979186","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}