Hooked on mushrooms:Preparation and mechanics of a bioinspired soft probabilistic fastener

Probabilistic fasteners are known to provide strong attachment onto their respective surfaces. Examples are Velcro® and the "3M dual lock"system. However, these systems typically only function using specific counter surfaces and are often destructive to other surfaces such as fabrics. Moreover, the design parameters to optimize their functionality are not obvious. Here, we present a surface patterned with soft micrometric features inspired by the mushroom shape showing a nondestructive mechanical interlocking and thus attachment to fabrics. We provide a scalable experimental approach to prepare these surfaces and quantify the attachment strength with rheometric and video-based analysis. In these "probabilistic fasteners,"we find that higher feature densities result in higher attachment force; however, the individual feature strength is higher on a low feature density surface. We interpret our results via a load-sharing principle common in fiber bundle models. Our work provides new handles for tuning the mechanical attachment properties of soft patterned surfaces that can be used in various applications including soft robotics.</p

Using Remote Access for Sharing Experiences in a Machine Design Laboratory

A new Machine Design Laboratory at Marquette University has been created to foster student exploration and promote “hands-on” and “minds-on” learning. Laboratory experiments have been developed to give students practical experiences and expose them to physical hardware, actual tools, and design challenges. Students face a range of real-world tasks: identify and select components, measure parameters (dimensions, speed, force), distinguish between normal and used (worn) components and between proper and abnormal behavior, reverse engineer systems, and justify design choices. The experiments serve to motivate the theory, spark interest, and promote discovery learning in the subject of machine design. This paper presents details of the experiments in the Machine Design Laboratory and then explores the feasibility of sharing some of the experiences with students at other institutions through remote access technologies. The paper proposes steps towards achieving this goal and raises issues to be addressed for a pilot-study offering machine design experiences to students globally who have access to the internet

Discovering electron transfer driven changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O)

Understanding the nature of chemical bonding in solids is crucial to comprehend the physical and chemical properties of a given compound. To explore changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O), a combination of property-, bond breaking- and quantum-mechanical bonding descriptors have been applied. The outcome of our explorations reveals an electron transfer driven transition from metavalent bonding in PbX (X = Te, Se, S) to iono-covalent bonding in beta-PbO. Metavalent bonding is characterized by adjacent atoms being held together by sharing about a single electron and small electron transfer (ET). The transition from metavalent to iono-covalent bonding manifests itself in clear changes in these quantum-mechanical descriptors (ES and ET), as well as in property-based descriptors (i.e. Born effective charge, dielectric function, effective coordination number (ECON) and mode-specific Grueneisen parameter, and in bond breaking descriptors (PME). Metavalent bonding collapses, if significant charge localization occurs at the ion cores (ET) and/or in the interatomic region (ES). Predominantly changing the degree of electron transfer opens possibilities to tailor materials properties such as the chemical bond and electronic polarizability, optical band gap and optical interband transitions characterized by the imaginary part of the dielectric function. Hence, the insights gained from this study highlight the technological relevance of the concept of metavalent bonding and its potential for materials design

Maximum Effectiveness of Electrostatic Energy Harvesters When Coupled to Interface Circuits

Accepted versio

Generic PLM system for SMEs: Application to an equipment manufacturer

For several years, digital engineering has increasingly taken a more important place in the strategic issues of mechanical engineering companies. Our proposition is an approach that enables technical data to be managed and used throughout the product life-cycle. This approach aims to provide assistance for costing, development and industrialization of the product, and for the capitalization, the reuse and the extension of fundamental knowledge. This approach has been experimented within several companies. This paper presents the case in a company environment that designs and produces families of ship equipment parts

Multiobjective analysis for the design and control of an electromagnetic valve actuator

The electromagnetic valve actuator can deliver much improved fuel efficiency and reduced emissions in spark ignition (SI) engines owing to the potential for variable valve timing when compared with cam-operated, or conventional, variable valve strategies. The possibility exists to reduce pumping losses by throttle-free operation, along with closed-valve engine braking. However, further development is required to make the technology suitable for accept- ance into the mass production market. This paper investigates the application of multiobjective optimization techniques to the conflicting objective functions inherent in the operation of such a device. The techniques are utilized to derive the optimal force–displacement characteristic for the solenoid actuator, along with its controllability and dynamic/steady state performance

Optimal Control Design for Multiterminal HVDC

This thesis proposes an optimal-control based design for distributed frequency control in multi-terminal high voltage direct current (MTDC) systems. The current power grid has become overstressed by rapid growth in the demand for electric power and penetration of renewable energy. To address these challenges, MTDC technology has been developed, which has the potential to increase the flexibility and reliability of power transmission in the grid. Several control strategies have been proposed to regulate the MTDC system and its interaction with connected AC systems. However, all the existing control strategies are based on proportional and integral (PI) control with predetermined controller structures. The objective of the thesis is to first determine if existing control structures are optimal, and if improved controller structures can be developed.The thesis proposes a general framework to determine the optimal structure for the control system in MTDC transmission through optimal feedback control. The proposed method is validated and demonstrated using an example of frequency control in a MTDC system connecting five AC areas