Browsing by Author "Gao, J."

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    Battle of the Water Calibration Networks
    (American Society of Civil Engineers, 2011) Ostfeld, A.; Salomons, E.; Ormsbee, L.; Uber, J.; Bros, C.; Kalungi, P.; Burd, R.; Zazula-Coetzee, B.; Belrain, T.; Kang, D.; Lansey, K.; Shen, H.; McBean, E.; Yi Wu, Z.; Walski, T.; Alvisi, S.; Franchini, M.; Johnson, J.; Ghimire, S.; Barkdoll, B.; Koppel, T.; Vassiljev, A.; Kim, J.; Chung, G.; Yoo, D.; Diao, Kegong; Zhou, Y.; Li, J.; Liu, Z.; Chang, K.; Gao, J.; Qu, S.; Yuan, Y.; Prasad, T.; Laucelli, D.; Vamvakeridou Lyroudia, L.; Kapelan, Z.; Savic, D.; Berardi, L.; Barbaro, G.; Giustolisi, O.; Asadzadeh, M.; Tolson, B.; McKillop, R.
    Calibration is a process of comparing model results with field data and making the appropriate adjustments so that both results agree. Calibration methods can involve formal optimization methods or manual methods in which the modeler informally examines alternative model parameters. The development of a calibration framework typically involves the following: (1) definition of the model variables, coefficients, and equations; (2) selection of an objective function to measure the quality of the calibration; (3) selection of the set of data to be used for the calibration process; and (4) selection of an optimization/manual scheme for altering the coefficient values in the direction of reducing the objective function. Hydraulic calibration usually involves the modification of system demands, fine-tuning the roughness values of pipes, altering pump operation characteristics, and adjusting other model attributes that affect simulation results, in particular those that have significant uncertainty associated with their values. From the previous steps, it is clear that model calibration is neither unique nor a straightforward technical task. The success of a calibration process depends on the modeler’s experience and intuition, as well as on the mathematical model and procedures adopted for the calibration process. This paper provides a summary of the Battle of the Water Calibration Networks (BWCN), the goal of which was to objectively compare the solutions of different approaches to the calibration of water distribution systems through application to a real water distribution system. Fourteen teams from academia, water utilities, and private consultants participated. The BWCN outcomes were presented and assessed at the 12th Water Distribution Systems Analysis conference in Tucson, Arizona, in September 2010. This manuscript summarizes the BWCN exercise and suggests future research directions for the calibration of water distribution systems.
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    Controlling Self-Assembling Peptide Hydrogel Properties through Network Topology
    (ACS, 2017-01-09) Gao, J.; Tang, C.; Elsawy, M.; Smith, A.; Miller, A.; Saiani, A.
    Self-assembling peptide-based hydrogels have encountered increasing interest in the recent years as scaffolds for 3D cell culture or for controlled drug delivery. One of the main challenges is the fine control of the mechanical properties of these materials. The bulk properties of hydrogels not only depend on the intrinsic properties of the fibers but also on the network topology formed. In this work we show how fiber−fiber interactions can be manipulated by design to control the final hydrogel network topology and therefore control the final properties of the material. This was achieved by exploiting the design features of β-sheet forming peptides based on hydrophobic and hydrophilic residue alternation and exploiting the ability of the arginine’s guanidine side group to interact with itself and with other amino acid side groups. By designing octa-peptides based on phenylalanine, glutamic acid, lysine, and arginine, we have investigated how fiber association and bundling affect the dynamic shear modulus of hydrogels and how it can be controlled by design. This work opens the possibility to fine-tune by design the bulk properties of peptide hydrogels.