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.

The Load as an Energy Asset in a Distributed DC SmartGrid Architecture

Abstract: DC power systems can be made more reliable by considering the load as an important energy asset. Currently the ability to manage the total system is available only through a centralized controller, which limits flexibility, reconfigurability, and reliability. These limitations can be avoided while still providing system level coordination through the use of distributed controls based on local information. All elements of the power system including source, loads, and the network itself have influence, interaction, and coupling to all other elements. Therefore, it is necessary to model and control a microgrid as a system of systems that share some common aspects, such as voltage levels, but can operate independently. Using local information in the form of the bus voltage, these techniques do not rely on a centralized controller, which improves system reliability. However, it is important to design the microgrid in such a manner as to take advantage of the energy not just from the generation sources, but also the energy stored in the individual points-of-load as well.

In situ electrochemical lithiation/delithiation observation of individual amorphous Si nanorods

Abstract: In situ electrochemical lithiation and delithiation processes inside a nanobattery consisting of an individual amorphous Si nanorod and ionic liquid were explored. Direct formation of the crystalline Li22Si5 phase due to the intercalation of Li ions was observed. In addition, the role of the electrolyte–nanorod interface was examined. It was observed that the lithiation of Si nanorods is dominated by surface diffusion. Upon the delithiation process, partial decomposition of Li22Si5 particles was observed which can explain the irreversible capacity loss that is generally seen in Si anodes. This study shows that the radial straining due to lithiation does not cause cracking in nanorods as small in diameter as 26 nm, whereas cracks were observed during the lithiation of 55 nm Si nanorods.

Improving the ratio of memory operations to floating-point operations in loops

Abstract: Over the past decade, microprocessor design strategies have focused on increasing the computational power on a single chip. Because computations often require more data from cache per floating-point operation than a machine can deliver and because operations are pipelined, idle computational cycles are common when scientific applications are executed. To overcome these bottlenecks, programmers have learned to use a coding style that ensures a better balance between memory references and floating-point operations. In our view, this is a step in the wrong direction because it makes programs more machine-specific. A programmer should not be required to write a new program version for each new machine; instead, the task of specializing a program to a target machine should be left to the compiler.But is our view practical? Can a sophisticated optimizing compiler obviate the need for the myriad of programming tricks that have found their way into practice to improve the performance of the memory hierarchy? In this paper we attempt to answer that question. To do so, we develop and evaluate techniques that automatically restructure program loops to achieve high performance on specific target architectures. These methods attempt to balance computation and memory accesses and seek to eliminate or reduce pipeline interlock. To do this, they estimate statically the balance between memory operations and floating-point operations for each loop in a particular program and use these estimates to determine whether to apply various loop transformations.Experiments with our automatic techniques show that integer-factor speedups are possible on kernels. Additionally, the estimate of the balance between memory operations and computation, and the application of the estimate are very accurate—experiments reveal little difference between the balance achieved by our automatic system that is made possible by hand optimization.

Regeneration of northern red oak: positive and negative effects of competitor removal

Abstract: The decreased ability of northern red oak (Quercus rubra) to regenerate throughout its range in the eastern United States has important ecological and economic implications. We studied regeneration of northern red oak in oak and pine stands on moderately productive sites in northern Lower Michigan. Our objectives were (1) to investigate the hypothesis that regeneration of northern red oak is more successful in pine than in oak stands and (2) to test whether removal of potential overstory and understory competitors increases regeneration success on moderately productive sites. Northern red oak acorns and 2-yr-old nursery seedlings were planted in spring 1991 in three natural oak stands and three red pine (Pinus resinosa) plantations on comparable, moderately productive sites. Each stand contained four canopy cover treatments: clearcut, 25% cover (50% the first year), 75% cover, and uncut. Each canopy cover treatment contained four understory treatments: herb-layer removal, shrub-layer removal, litter remov...