Effects of Gradually Anchored Prestressed CFRP Strips Bonded on Prestressed Concrete Beams

Four prestressed concrete beams were constructed and tested to investigate the effectiveness of flexural post-strengthening with prestressed carbon fiber-reinforced polymer (CFRP) strips. One of the beams served as a reference beam, another was bonded with an unstressed CFRP strip, and the remaining two specimens were strengthened with prestressed CFRP strips at two prestressing levels. The gradient method was used for the anchorage of the prestressed CFRP strips. Experimental and analytical calculations are compared with the test results. Further, different failure modes are explained. On the basis of this investigation, recommendations for the use of prestressed CFRP strips anchored with the gradient method are given.     

Hormone-Inspired Self-Organization and Distributed Control of Robotic Swarms

The control of robot swarming in a distributed manner is a difficult problem because global behaviors must emerge as a result of many local actions. This paper uses a bio-inspired control method called the Digital Hormone Model (DHM) to control the tasking and executing of robot swarms based on local communication, signal propagation, and stochastic reactions. The DHM model is probabilistic, dynamic, fault-tolerant, computationally efficient, and can be easily tasked to change global behavior. Different from most existing distributed control and learning mechanisms, DHM considers the topological structure of the organization, supports dynamic reconfiguration and self-organization, and requires no globally unique identifiers for individual robots. The paper describes the DHM and presents the experimental results on simulating biological observations in the forming of feathers, and simulating wireless communicated swarm behavior at a large scale for attacking target, forming sensor networks, self-repairing, and avoiding pitfalls in mission execution.     

Thermoresponsive hyperbranched copolymer with multi acrylate functionality for in situ cross-linkable hyaluronic acid composite semi-IPN hydrogel

Thermoresponsive polymers have been widely used for in situ formed hydrogels in drug delivery and tissue engineering as they are easy to handle and their shape can easily conform to tissue defects. However, non-covalent bonding and mechanical weakness of these hydrogels limit their applications. In this study, a physically and chemically in situ cross-linkable hydrogel system was developed from a novel thermoresponsive hyperbranched PEG based copolymer with multi acrylate functionality, which was synthesized via an ‘one pot and one step’ in situ deactivation enhanced atom transfer radical co-polymerization of poly(ethylene glycol) diacrylate (PEGDA, M_n = 258 g mol⁻¹), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA, M_n = 475 g mol⁻¹) and (2-methoxyethoxy) ethyl methacrylate (MEO₂MA). This hyperbranched copolymer was tailored to have the lower critical solution temperature to form physical gelation around 37°C. Meanwhile, with high level of acrylate functionalities, a chemically cross-linked gel was formed from this copolymer using thiol functional cross-linker of pentaerythritol tetrakis (3-mercaptopropionate) (QT) via thiol-ene Michael addition reaction. Furthermore, a semi-interpenetrated polymer networks (semi-IPN) structure was developed by combining this polymer with hyaluronic acid (HA), leading to an in situ cross-linkable hydrogel with significantly increased porosity, enhanced swelling behavior and improved cell adhesion and viability both in 2D and 3D cell culture models.     

Invited Paper: Surface‐emitting‐diode lasers and laser arrays for displays

Abstract— High‐power red, green, and blue laser light sources made from vertically emitting arrays of intracavity doubled IR lasers is reported. The emitted infrared light from a monolithic array of large‐aperture vertical cavity lasers is converted into visible light using a PPLN doubling crystal in an external cavity. A volume Bragg grating provides simultaneous feedback for all emitters in the array and sets the laser wavelength. Increased diffraction losses for higher‐order modes result in quasi‐Gaussian beams with excellent conversion efficiency. Green 532‐nm lasers with more than 5.8‐W visible power have been demonstrated at a base temperature of 40°C. Blue 465‐nm lasers with 4.4‐W power at 40°C are unmatched in performance and wavelength when compared to competing GaN‐based edge emitters. Typical wall‐plug efficiencies are higher than 8%. We have measured single‐emitter operating lifetimes to be more than 28,000 hours. Red lasers based on highly strained InGaAs achieve record laser powers of 2.0W at 618 nm in the same form factor as the green and blue lasers. Red single‐emitter lifetimes of more than 10,000 hours have been attained. The technology described in this paper delivers on a full suite of cost efficient and reliable red, green, and blue lasers that meet the demands of the display markets.