Purdue University

About: Purdue University is a education organization based out in West Lafayette, Indiana, United States. It is known for research contribution in the topics: Population & Context (language use). The organization has 73219 authors who have published 163563 publications receiving 5775236 citations. The organization is also known as: Purdue & Purdue-West Lafayette.

A Higher Order Closure Model for Canopy Flow

Abstract: The equations of motion were used to develop a one-dimensional, nonbuoyant mathematical model of air flow within vegetative canopies. The model consists of equations for mean horizontal momentum, Reynolds stress, and for the three components of turbulent kinetic energy with closure achieved by parameterizing the higher order terms. This eliminates the need to model the Reynolds stress directly using an eddy viscosity. The closure schemes rely upon a prescribed length scale and have been used elsewhere in modeling the atmospheric boundary layer free of vegetation. The equations were solved numerically using specified boundary conditions. Using a profile of plant area density for a crop of corn (Zea mays L.) the model predicted mean wind velocity, Reynolds stress and turbulent intensities for the region from the soil surface to twice the canopy height that compare well with experimental measurements (Shaw et al., 1974a,b). The model is believed to overestimate the intensity of turbulence generated ...

Activation of EphA2 kinase suppresses integrin function and causes focal-adhesion-kinase dephosphorylation

Abstract: Interactions between receptor tyrosine kinases of the Eph family and their ligands, ephrins, are implicated in establishment of organ boundaries and repulsive guidance of cell migration during development, but the mechanisms by which this is achieved are unclear Here we show that activation of endogenous EphA2 kinase induces an inactive conformation of integrins and inhibits cell spreading, migration and integrin-mediated adhesion Moreover, EphA2 is constitutively associated with focal-adhesion kinase (FAK) in resting cells Within one minute after stimulation of EphA2 with its ligand, ephrin-A1, the protein tyrosine phosphatase SHP2 is recruited to EphA2; this is followed by dephosphorylation of FAK and paxillin, and dissociation of the FAK-EphA2 complex We conclude that Eph kinases mediate some of their functions by negatively regulating integrins and FAK

Robust and Secure Wireless Communications via Intelligent Reflecting Surfaces

Abstract: In this paper, intelligent reflecting surfaces (IRSs) are employed to enhance the physical layer security in a challenging radio environment. In particular, a multi-antenna access point (AP) has to serve multiple single-antenna legitimate users, which do not have line-of-sight communication links, in the presence of multiple multi-antenna potential eavesdroppers whose channel state information (CSI) is not perfectly known. Artificial noise (AN) is transmitted from the AP to deliberately impair the eavesdropping channels for security provisioning. We investigate the joint design of the beamformers and AN covariance matrix at the AP and the phase shifters at the IRSs for maximization of the system sum-rate while limiting the maximum information leakage to the potential eavesdroppers. To this end, we formulate a robust non-convex optimization problem taking into account the impact of the imperfect CSI of the eavesdropping channels. To address the non-convexity of the optimization problem, an efficient algorithm is developed by capitalizing on alternating optimization, a penalty-based approach, successive convex approximation, and semidefinite relaxation. Simulation results show that IRSs can significantly improve the system secrecy performance compared to conventional architectures without IRS. Furthermore, our results unveil that, for physical layer security, uniformly distributing the reflecting elements among multiple IRSs is preferable over deploying them at a single IRS.

A Structural Analysis of Disappointment Aversion in a Real Effort Competition

Abstract: We develop a novel computerized real effort task, based on moving sliders across a screen, to test experimentally whether agents are disappointment averse when they compete in a real effort sequential-move tournament. Our theory predicts that a disappointment averse agent, who is loss averse around her endogenous expectations-based reference point, responds negatively to her rival's effort. We find significant evidence for this discouragement effect, and use the Method of Simulated Moments to estimate the strength of disappointment aversion on average and the heterogeneity in disappointment aversion across the population.