[{"page":"114","ddc":["004","005","006","532","621"],"date_updated":"2024-02-21T13:50:48Z","_id":"1122","type":"dissertation","doi":"10.15479/AT:ISTA:th_640","article_processing_charge":"No","alternative_title":["ISTA Thesis"],"publisher":"Institute of Science and Technology Austria","acknowledgement":"First and foremost I would like to thank Chris. I have been incredibly lucky to have\r\nyou as my advisor. Your integrity and aspiration to do the right thing in all walks of\r\nlife is something I admire and aspire to. I also really appreciate the fact that when\r\nworking with you it felt like we were equals. I think we had a very synergetic work\r\nrelationship: I learned immensely from you, but I dare say that you learned a few\r\nthings from me as well. ;)\r\nNext, I would like to thank my amazing committee. Hao, it was a fantastic\r\nexperience working with you. You showed me how to persevere and keep morale\r\nhigh when things were looking the most bleak before the deadline. You are an\r\nincredible motivator and super fun to be around! Vladimir, thanks for the shared\r\nlunches and the poker games. Sorry for not bringing them back when I got busy.\r\nAlso, sorry for embarrassing you by asking about your guitar playing that one\r\ntime. You really are quite awesome! Nils, one of the friendliest and most humble\r\npeople you will meet and a top notch researcher to boot! Thank you for joining\r\nmy committee late!\r\nI would also like to acknowledge the Visual Computing group at IST Austria\r\nfrom whom I have learned so much. The excellent discussions we had in reading\r\ngroups and research meetings really helped me become a better researcher!\r\nNext, I would like to thank all the amazing people that I met during my PhD\r\nstudies, both at IST Austria, in Vienna and elsewhere. ","date_published":"2016-07-15T00:00:00Z","degree_awarded":"PhD","status":"public","publist_id":"6238","year":"2016","related_material":{"record":[{"status":"public","relation":"other","id":"5558"}]},"publication_identifier":{"issn":["2663-337X"]},"publication_status":"published","file_date_updated":"2018-12-12T10:13:02Z","has_accepted_license":"1","abstract":[{"text":"Computer graphics is an extremely exciting field for two reasons. On the one hand,\r\nthere is a healthy injection of pragmatism coming from the visual effects industry\r\nthat want robust algorithms that work so they can produce results at an increasingly\r\nfrantic pace. On the other hand, they must always try to push the envelope and\r\nachieve the impossible to wow their audiences in the next blockbuster, which means\r\nthat the industry has not succumb to conservatism, and there is plenty of room to\r\ntry out new and crazy ideas if there is a chance that it will pan into something\r\nuseful.\r\nWater simulation has been in visual effects for decades, however it still remains\r\nextremely challenging because of its high computational cost and difficult artdirectability.\r\nThe work in this thesis tries to address some of these difficulties.\r\nSpecifically, we make the following three novel contributions to the state-of-the-art\r\nin water simulation for visual effects.\r\nFirst, we develop the first algorithm that can convert any sequence of closed\r\nsurfaces in time into a moving triangle mesh. State-of-the-art methods at the time\r\ncould only handle surfaces with fixed connectivity, but we are the first to be able to\r\nhandle surfaces that merge and split apart. This is important for water simulation\r\npractitioners, because it allows them to convert splashy water surfaces extracted\r\nfrom particles or simulated using grid-based level sets into triangle meshes that can\r\nbe either textured and enhanced with extra surface dynamics as a post-process.\r\nWe also apply our algorithm to other phenomena that merge and split apart, such\r\nas morphs and noisy reconstructions of human performances.\r\nSecond, we formulate a surface-based energy that measures the deviation of a\r\nwater surface froma physically valid state. Such discrepancies arise when there is a\r\nmismatch in the degrees of freedom between the water surface and the underlying\r\nphysics solver. This commonly happens when practitioners use a moving triangle\r\nmesh with a grid-based physics solver, or when high-resolution grid-based surfaces\r\nare combined with low-resolution physics. Following the direction of steepest\r\ndescent on our surface-based energy, we can either smooth these artifacts or turn\r\nthem into high-resolution waves by interpreting the energy as a physical potential.\r\nThird, we extend state-of-the-art techniques in non-reflecting boundaries to handle spatially and time-varying background flows. This allows a novel new\r\nworkflow where practitioners can re-simulate part of an existing simulation, such\r\nas removing a solid obstacle, adding a new splash or locally changing the resolution.\r\nSuch changes can easily lead to new waves in the re-simulated region that would\r\nreflect off of the new simulation boundary, effectively ruining the illusion of a\r\nseamless simulation boundary between the existing and new simulations. Our\r\nnon-reflecting boundaries makes sure that such waves are absorbed.","lang":"eng"}],"tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"date_created":"2018-12-11T11:50:16Z","author":[{"last_name":"Bojsen-Hansen","full_name":"Bojsen-Hansen, Morten","id":"439F0C8C-F248-11E8-B48F-1D18A9856A87","first_name":"Morten","orcid":"0000-0002-4417-3224"}],"day":"15","title":"Tracking, correcting and absorbing water surface waves","oa_version":"Published Version","citation":{"ista":"Bojsen-Hansen M. 2016. Tracking, correcting and absorbing water surface waves. Institute of Science and Technology Austria.","chicago":"Bojsen-Hansen, Morten. “Tracking, Correcting and Absorbing Water Surface Waves.” Institute of Science and Technology Austria, 2016. <a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">https://doi.org/10.15479/AT:ISTA:th_640</a>.","apa":"Bojsen-Hansen, M. (2016). <i>Tracking, correcting and absorbing water surface waves</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">https://doi.org/10.15479/AT:ISTA:th_640</a>","mla":"Bojsen-Hansen, Morten. <i>Tracking, Correcting and Absorbing Water Surface Waves</i>. Institute of Science and Technology Austria, 2016, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">10.15479/AT:ISTA:th_640</a>.","ama":"Bojsen-Hansen M. Tracking, correcting and absorbing water surface waves. 2016. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">10.15479/AT:ISTA:th_640</a>","ieee":"M. Bojsen-Hansen, “Tracking, correcting and absorbing water surface waves,” Institute of Science and Technology Austria, 2016.","short":"M. Bojsen-Hansen, Tracking, Correcting and Absorbing Water Surface Waves, Institute of Science and Technology Austria, 2016."},"user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","oa":1,"language":[{"iso":"eng"}],"department":[{"_id":"ChWo"}],"file":[{"date_updated":"2018-12-12T10:13:02Z","creator":"system","file_size":13869345,"date_created":"2018-12-12T10:13:02Z","file_id":"4982","content_type":"application/pdf","access_level":"open_access","file_name":"IST-2016-640-v1+1_2016_Bojsen-Hansen_TCaAWSW.pdf","relation":"main_file"}],"supervisor":[{"id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87","full_name":"Wojtan, Christopher J","last_name":"Wojtan","first_name":"Christopher J","orcid":"0000-0001-6646-5546"}],"month":"07"},{"file_date_updated":"2020-07-14T12:47:02Z","ddc":["004"],"tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"abstract":[{"text":"PhD thesis LaTeX source code","lang":"eng"}],"has_accepted_license":"1","date_created":"2018-12-12T12:31:31Z","type":"research_data","_id":"5558","date_updated":"2024-02-21T13:50:48Z","oa_version":"Published Version","title":"Tracking, Correcting and Absorbing Water Surface Waves","publisher":"Institute of Science and Technology Austria","day":"23","article_processing_charge":"No","doi":"10.15479/AT:ISTA:48","author":[{"orcid":"0000-0002-4417-3224","first_name":"Morten","last_name":"Bojsen-Hansen","full_name":"Bojsen-Hansen, Morten","id":"439F0C8C-F248-11E8-B48F-1D18A9856A87"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","date_published":"2016-09-23T00:00:00Z","citation":{"ama":"Bojsen-Hansen M. Tracking, Correcting and Absorbing Water Surface Waves. 2016. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:48\">10.15479/AT:ISTA:48</a>","short":"M. Bojsen-Hansen, (2016).","ieee":"M. Bojsen-Hansen, “Tracking, Correcting and Absorbing Water Surface Waves.” Institute of Science and Technology Austria, 2016.","ista":"Bojsen-Hansen M. 2016. Tracking, Correcting and Absorbing Water Surface Waves, Institute of Science and Technology Austria, <a href=\"https://doi.org/10.15479/AT:ISTA:48\">10.15479/AT:ISTA:48</a>.","chicago":"Bojsen-Hansen, Morten. “Tracking, Correcting and Absorbing Water Surface Waves.” Institute of Science and Technology Austria, 2016. <a href=\"https://doi.org/10.15479/AT:ISTA:48\">https://doi.org/10.15479/AT:ISTA:48</a>.","mla":"Bojsen-Hansen, Morten. <i>Tracking, Correcting and Absorbing Water Surface Waves</i>. Institute of Science and Technology Austria, 2016, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:48\">10.15479/AT:ISTA:48</a>.","apa":"Bojsen-Hansen, M. (2016). Tracking, Correcting and Absorbing Water Surface Waves. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:48\">https://doi.org/10.15479/AT:ISTA:48</a>"},"datarep_id":"48","status":"public","pubrep_id":"640","oa":1,"file":[{"date_updated":"2020-07-14T12:47:02Z","creator":"system","file_size":55237885,"date_created":"2018-12-12T13:02:18Z","file_id":"5589","content_type":"application/x-bzip2","access_level":"open_access","file_name":"IST-2016-48-v1+1_2016_Bojsen-Hansen_TCaAWSW.tar.bz2","checksum":"5b1b256ad796fbddb4b7729f5e45e444","relation":"main_file"}],"publist_id":"6238","department":[{"_id":"ChWo"}],"month":"09","related_material":{"record":[{"status":"public","relation":"other","id":"1122"}]},"year":"2016"},{"publist_id":"5879","year":"2016","ec_funded":1,"date_published":"2016-07-11T00:00:00Z","acknowledgement":"We thank the IST Austria Visual Computing group for helpful feedback throughout the project. ","conference":{"location":"Anaheim, CA, USA","start_date":"2016-07-24","end_date":"2016-07-28","name":"ACM SIGGRAPH"},"status":"public","project":[{"_id":"2533E772-B435-11E9-9278-68D0E5697425","call_identifier":"H2020","name":"Efficient Simulation of Natural Phenomena at Extremely Large Scales","grant_number":"638176"}],"_id":"1363","date_updated":"2023-02-21T10:36:12Z","type":"conference","alternative_title":["ACM Transactions on Graphics"],"doi":"10.1145/2897824.2925963","publisher":"ACM","quality_controlled":"1","ddc":["000"],"department":[{"_id":"ChWo"}],"article_number":"96","file":[{"checksum":"140b5532f0a2a006a0149cab7c73c17c","relation":"main_file","content_type":"application/pdf","access_level":"open_access","file_name":"IST-2016-631-v1+2_a96-bojsen-hansen.pdf","file_id":"4981","date_updated":"2020-07-14T12:44:47Z","creator":"system","file_size":12422760,"date_created":"2018-12-12T10:13:00Z"}],"month":"07","citation":{"ista":"Bojsen-Hansen M, Wojtan C. 2016. Generalized non-reflecting boundaries for fluid re-simulation. ACM SIGGRAPH, ACM Transactions on Graphics, vol. 35, 96.","chicago":"Bojsen-Hansen, Morten, and Chris Wojtan. “Generalized Non-Reflecting Boundaries for Fluid Re-Simulation,” Vol. 35. ACM, 2016. <a href=\"https://doi.org/10.1145/2897824.2925963\">https://doi.org/10.1145/2897824.2925963</a>.","mla":"Bojsen-Hansen, Morten, and Chris Wojtan. <i>Generalized Non-Reflecting Boundaries for Fluid Re-Simulation</i>. Vol. 35, no. 4, 96, ACM, 2016, doi:<a href=\"https://doi.org/10.1145/2897824.2925963\">10.1145/2897824.2925963</a>.","apa":"Bojsen-Hansen, M., &#38; Wojtan, C. (2016). Generalized non-reflecting boundaries for fluid re-simulation (Vol. 35). Presented at the ACM SIGGRAPH, Anaheim, CA, USA: ACM. <a href=\"https://doi.org/10.1145/2897824.2925963\">https://doi.org/10.1145/2897824.2925963</a>","ama":"Bojsen-Hansen M, Wojtan C. Generalized non-reflecting boundaries for fluid re-simulation. In: Vol 35. ACM; 2016. doi:<a href=\"https://doi.org/10.1145/2897824.2925963\">10.1145/2897824.2925963</a>","short":"M. Bojsen-Hansen, C. Wojtan, in:, ACM, 2016.","ieee":"M. Bojsen-Hansen and C. Wojtan, “Generalized non-reflecting boundaries for fluid re-simulation,” presented at the ACM SIGGRAPH, Anaheim, CA, USA, 2016, vol. 35, no. 4."},"issue":"4","user_id":"4435EBFC-F248-11E8-B48F-1D18A9856A87","oa":1,"pubrep_id":"631","language":[{"iso":"eng"}],"volume":35,"date_created":"2018-12-11T11:51:35Z","day":"11","author":[{"first_name":"Morten","orcid":"0000-0002-4417-3224","last_name":"Bojsen-Hansen","id":"439F0C8C-F248-11E8-B48F-1D18A9856A87","full_name":"Bojsen-Hansen, Morten"},{"orcid":"0000-0001-6646-5546","first_name":"Christopher J","last_name":"Wojtan","full_name":"Wojtan, Christopher J","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87"}],"oa_version":"Published Version","title":"Generalized non-reflecting boundaries for fluid re-simulation","file_date_updated":"2020-07-14T12:44:47Z","publication_status":"published","has_accepted_license":"1","acknowledged_ssus":[{"_id":"ScienComp"}],"intvolume":"        35","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"abstract":[{"lang":"eng","text":"When aiming to seamlessly integrate a fluid simulation into a larger scenario (like an open ocean), careful attention must be paid to boundary conditions. In particular, one must implement special &quot;non-reflecting&quot; boundary conditions, which dissipate out-going waves as they exit the simulation. Unfortunately, the state of the art in non-reflecting boundary conditions (perfectly-matched layers, or PMLs) only permits trivially simple inflow/outflow conditions, so there is no reliable way to integrate a fluid simulation into a more complicated environment like a stormy ocean or a turbulent river. This paper introduces the first method for combining nonreflecting boundary conditions based on PMLs with inflow/outflow boundary conditions that vary arbitrarily throughout space and time. Our algorithm is a generalization of stateof- the-art mean-flow boundary conditions in the computational fluid dynamics literature, and it allows for seamless integration of a fluid simulation into much more complicated environments. Our method also opens the door for previously-unseen postprocess effects like retroactively changing the location of solid obstacles, and locally increasing the visual detail of a pre-existing simulation."}]},{"issue":"4","citation":{"short":"M. Bojsen-Hansen, C. Wojtan, ACM Transactions on Graphics 32 (2013).","ieee":"M. Bojsen-Hansen and C. Wojtan, “Liquid surface tracking with error compensation,” <i>ACM Transactions on Graphics</i>, vol. 32, no. 4. ACM, 2013.","ama":"Bojsen-Hansen M, Wojtan C. Liquid surface tracking with error compensation. <i>ACM Transactions on Graphics</i>. 2013;32(4). doi:<a href=\"https://doi.org/10.1145/2461912.2461991\">10.1145/2461912.2461991</a>","mla":"Bojsen-Hansen, Morten, and Chris Wojtan. “Liquid Surface Tracking with Error Compensation.” <i>ACM Transactions on Graphics</i>, vol. 32, no. 4, 68, ACM, 2013, doi:<a href=\"https://doi.org/10.1145/2461912.2461991\">10.1145/2461912.2461991</a>.","apa":"Bojsen-Hansen, M., &#38; Wojtan, C. (2013). Liquid surface tracking with error compensation. <i>ACM Transactions on Graphics</i>. ACM. <a href=\"https://doi.org/10.1145/2461912.2461991\">https://doi.org/10.1145/2461912.2461991</a>","chicago":"Bojsen-Hansen, Morten, and Chris Wojtan. “Liquid Surface Tracking with Error Compensation.” <i>ACM Transactions on Graphics</i>. ACM, 2013. <a href=\"https://doi.org/10.1145/2461912.2461991\">https://doi.org/10.1145/2461912.2461991</a>.","ista":"Bojsen-Hansen M, Wojtan C. 2013. Liquid surface tracking with error compensation. ACM Transactions on Graphics. 32(4), 68."},"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa":1,"pubrep_id":"603","language":[{"iso":"eng"}],"department":[{"_id":"ChWo"}],"article_number":"68","file":[{"content_type":"application/pdf","access_level":"open_access","file_name":"IST-2016-603-v1+1_liquidError_web.pdf","checksum":"53d905e0180e23ef3e813b969ffed4e1","relation":"main_file","creator":"system","date_updated":"2020-07-14T12:45:41Z","date_created":"2018-12-12T10:09:37Z","file_size":5813685,"file_id":"4761"}],"month":"07","publication_status":"published","file_date_updated":"2020-07-14T12:45:41Z","has_accepted_license":"1","abstract":[{"text":"Our work concerns the combination of an Eulerian liquid simulation with a high-resolution surface tracker (e.g. the level set method or a Lagrangian triangle mesh). The naive application of a high-resolution surface tracker to a low-resolution velocity field can produce many visually disturbing physical and topological artifacts that limit their use in practice. We address these problems by defining an error function which compares the current state of the surface tracker to the set of physically valid surface states. By reducing this error with a gradient descent technique, we introduce a novel physics-based surface fairing method. Similarly, by treating this error function as a potential energy, we derive a new surface correction force that mimics the vortex sheet equations. We demonstrate our results with both level set and mesh-based surface trackers.","lang":"eng"}],"intvolume":"        32","volume":32,"date_created":"2018-12-11T11:57:50Z","author":[{"first_name":"Morten","orcid":"0000-0002-4417-3224","last_name":"Bojsen-Hansen","full_name":"Bojsen-Hansen, Morten","id":"439F0C8C-F248-11E8-B48F-1D18A9856A87"},{"last_name":"Wojtan","full_name":"Wojtan, Christopher J","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87","first_name":"Christopher J","orcid":"0000-0001-6646-5546"}],"day":"01","scopus_import":1,"title":"Liquid surface tracking with error compensation","oa_version":"Submitted Version","date_published":"2013-07-01T00:00:00Z","publication":"ACM Transactions on Graphics","status":"public","publist_id":"4434","year":"2013","quality_controlled":"1","ddc":["000"],"date_updated":"2023-02-23T10:44:18Z","_id":"2468","type":"journal_article","doi":"10.1145/2461912.2461991","publisher":"ACM"},{"abstract":[{"text":"We present a method for recovering a temporally coherent, deforming triangle mesh with arbitrarily changing topology from an incoherent sequence of static closed surfaces. We solve this problem using the surface geometry alone, without any prior information like surface templates or velocity fields. Our system combines a proven strategy for triangle mesh improvement, a robust multi-resolution non-rigid registration routine, and a reliable technique for changing surface mesh topology. We also introduce a novel topological constraint enforcement algorithm to ensure that the output and input always have similar topology. We apply our technique to a series of diverse input data from video reconstructions, physics simulations, and artistic morphs. The structured output of our algorithm allows us to efficiently track information like colors and displacement maps, recover velocity information, and solve PDEs on the mesh as a post process.","lang":"eng"}],"intvolume":"        31","has_accepted_license":"1","publication_status":"published","file_date_updated":"2020-07-14T12:46:00Z","title":"Tracking surfaces with evolving topology","oa_version":"Submitted Version","author":[{"last_name":"Bojsen-Hansen","full_name":"Bojsen-Hansen, Morten","id":"439F0C8C-F248-11E8-B48F-1D18A9856A87","first_name":"Morten","orcid":"0000-0002-4417-3224"},{"first_name":"Hao","last_name":"Li","full_name":"Li, Hao"},{"last_name":"Wojtan","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87","full_name":"Wojtan, Christopher J","first_name":"Christopher J","orcid":"0000-0001-6646-5546"}],"day":"01","scopus_import":"1","article_type":"original","date_created":"2018-12-11T12:01:29Z","volume":31,"language":[{"iso":"eng"}],"pubrep_id":"602","oa":1,"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","issue":"4","citation":{"ama":"Bojsen-Hansen M, Li H, Wojtan C. Tracking surfaces with evolving topology. <i>ACM Transactions on Graphics</i>. 2012;31(4). doi:<a href=\"https://doi.org/10.1145/2185520.2185549\">10.1145/2185520.2185549</a>","short":"M. Bojsen-Hansen, H. Li, C. Wojtan, ACM Transactions on Graphics 31 (2012).","ieee":"M. Bojsen-Hansen, H. Li, and C. Wojtan, “Tracking surfaces with evolving topology,” <i>ACM Transactions on Graphics</i>, vol. 31, no. 4. ACM, 2012.","chicago":"Bojsen-Hansen, Morten, Hao Li, and Chris Wojtan. “Tracking Surfaces with Evolving Topology.” <i>ACM Transactions on Graphics</i>. ACM, 2012. <a href=\"https://doi.org/10.1145/2185520.2185549\">https://doi.org/10.1145/2185520.2185549</a>.","ista":"Bojsen-Hansen M, Li H, Wojtan C. 2012. Tracking surfaces with evolving topology. ACM Transactions on Graphics. 31(4), 53.","mla":"Bojsen-Hansen, Morten, et al. “Tracking Surfaces with Evolving Topology.” <i>ACM Transactions on Graphics</i>, vol. 31, no. 4, 53, ACM, 2012, doi:<a href=\"https://doi.org/10.1145/2185520.2185549\">10.1145/2185520.2185549</a>.","apa":"Bojsen-Hansen, M., Li, H., &#38; Wojtan, C. (2012). Tracking surfaces with evolving topology. <i>ACM Transactions on Graphics</i>. ACM. <a href=\"https://doi.org/10.1145/2185520.2185549\">https://doi.org/10.1145/2185520.2185549</a>"},"month":"07","article_number":"53","file":[{"file_id":"5359","date_updated":"2020-07-14T12:46:00Z","creator":"system","date_created":"2018-12-12T10:18:37Z","file_size":44538518,"checksum":"1e219c5bf4e5552c1290c62eefa5cd60","relation":"main_file","access_level":"open_access","content_type":"application/pdf","file_name":"IST-2016-602-v1+1_topoReg.pdf"}],"department":[{"_id":"ChWo"}],"ddc":["000"],"quality_controlled":"1","publisher":"ACM","doi":"10.1145/2185520.2185549","alternative_title":["SIGGRAPH"],"article_processing_charge":"No","type":"journal_article","date_updated":"2022-05-24T08:21:11Z","_id":"3118","publication":"ACM Transactions on Graphics","status":"public","date_published":"2012-07-01T00:00:00Z","acknowledgement":"This work is supported by the SNF fellowship PBEZP2-134464.\r\nWe would like to thank Xiaochen Hu for implementing mesh con- version tools, Duygu Ceylan for helping with the rendering, and Art Tevs for the human performance data comparison. We also thank Nils Thuerey and Christopher Batty for helpful discussions. ","year":"2012","publist_id":"3581"}]