Michigan Technological University

About: Michigan Technological University is a education organization based out in Houghton, Michigan, United States. It is known for research contribution in the topics: Population & Volcano. The organization has 8023 authors who have published 17422 publications receiving 481780 citations. The organization is also known as: MTU & Michigan Tech.

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth

Abstract: The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera–electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera–electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

Hydrogen Storage in Metal–Organic Frameworks

Abstract: Metal-organic frameworks (MOFs) are highly attractive materials because of their ultra-high surface areas, simple preparation approaches, designable structures, and potential applications. In the past several years, MOFs have attracted worldwide attention in the area of hydrogen energy, particularly for hydrogen storage. In this review, the recent progress of hydrogen storage in MOFs is presented. The relationships between hydrogen capacities and structures of MOFs are evaluated, with emphasis on the roles of surface area and pore size. The interaction mechanism between H(2) and MOFs is discussed. The challenges to obtain a high hydrogen capacity at ambient temperature are explored.

Energy harvesting from a backpack instrumented with piezoelectric shoulder straps

Abstract: Over the past few decades the use of portable and wearable electronics has grown steadily These devices are becoming increasingly more powerful However, the gains that have been made in the device performance have resulted in the need for significantly higher power to operate the electronics This issue has been further complicated due to the stagnant growth of battery technology over the past decade In order to increase the life of these electronics, researchers have begun investigating methods of generating energy from ambient sources such that the life of the electronics can be prolonged Recent developments in the field have led to the design of a number of mechanisms that can be used to generate electrical energy, from a variety of sources including thermal, solar, strain, inertia, etc Many of these energy sources are available for use with humans, but their use must be carefully considered such that parasitic effects that could disrupt the user's gait or endurance are avoided These issues have arisen from previous attempts to integrate power harvesting mechanisms into a shoe such that the energy released during a heal strike could be harvested This study develops a novel energy harvesting backpack that can generate electrical energy from the differential forces between the wearer and the pack The goal of this system is to make the energy harvesting device transparent to the wearer such that his or her endurance and dexterity is not compromised This will be accomplished by replacing the traditional strap of the backpack with one made of the piezoelectric polymer polyvinylidene fluoride (PVDF) Piezoelectric materials have a structure such that an applied electrical potential results in a mechanical strain Conversely, an applied stress results in the generation of an electrical charge, which makes the material useful for power harvesting applications PVDF is highly flexible and has a high strength, allowing it to effectively act as the load bearing member In order to preserve the performance of the backpack and user, the design of the pack will be held as close to existing systems as possible This paper develops a theoretical model of the piezoelectric strap and uses experimental testing to identify its performance in this application