Yan Y.,University of Nottingham |
Yang S.,University of Nottingham |
Blake A.J.,University of Nottingham |
Lewis W.,University of Nottingham |
And 4 more authors.
Chemical Communications | Year: 2011
The mesoporous framework [Cu3(L)(H2O) 3]·(DMF)35·(H2O)35 (NOTT-119) shows on desolvation a BET surface area of 4118(200) m2 g-1, a pore volume of 2.35 cm3 g-1, a total H2 uptake of 101 mg g-1 at 60 bar, 77 K and a total CH4 uptake of 327 mg g-1 at 80 bar, 298 K. © The Royal Society of Chemistry 2011.
Khaitan S.K.,Iowa State University |
McCalley J.D.,Iowa State University |
Raju M.,Optimal Inc.
Energy Systems | Year: 2010
Newton-Raphson method is the most widely accepted load flow solution algorithm. However LU factorization remains a computationally challenging task to meet the real-time needs of the power system. This paper proposes the application of very fast multifrontal direct linear solvers for solving the linear system sub-problem of power system real-time load flow analysis by utilizing the state-of-the-art algorithms for ordering and preprocessing. Additionally the unsymmetric multifrontal method for LU factorization and highly optimized Intel® Math Kernel Library BLAS has been used. Two state-of-the-art multifrontal algorithms for unsymmetric matrices namely UMFPACK V5.2.0 and sequential MUMPS 4.8.3 ("Multifrontal Massively Parallel Solver") are customized for the AC power system Newton-Raphson based load flow analysis. The multifrontal solvers are compared against the state-of-the-art sparse Gaussian Elimination based HSL sparse solver MA48. This study evaluates the performance of above multifrontal solvers in terms of number of factors, computational time, number of floating-point operations and memory, in the context of load flow solution on nine systems including very large real power systems. The results of the performance evaluation are reported. The proposed method achieves significant reduction in computational time. © Springer-Verlag 2010.
Shi X.,General Motors |
Shi X.,Optimal Incorporated |
Yang J.,General Motors |
Bai S.,CAS Shanghai Institute of Ceramics |
And 7 more authors.
Advanced Functional Materials | Year: 2010
Type I clathrates have recently been identified as prospective thermoelectric materials for power generation purposes due to their very low lattice thermal conductivity values. The maximum thermoelectric figure of merit of almost all type I clathrates is, however, less than 1 and occurs at, or above, 1000 K, making them unfavorable especially for intermediate temperature applications. In this report, the Zintl-Klemm rule is demonstrated to be valid for Ni, Cu, and Zn transition metal substitution in the framework of type I clathrates and offers many degrees of freedom for material modification, design, and optimization. The cross-substitution of framework elements introduces ionized impurities and lattice defects into these materials, which optimize the scattering of charge carriers by the substitution-induced ionized impurities and the scattering of heat-carrying lattice phonons by point defects, respectively, leading to an enhanced power factor, reduced lattice thermal conductivity, and therefore improved thermoelectric figure of merit. Most importantly, the bandgap of these materials can be tuned between 0.1 and 0.5 eV by adjusting the cross-substitution ratio of framework elements, making it possible to design clathrates with excellent thermoelectric properties between 500 and 1000 K. © 2010 WILEY-VCH Verlag GmbH &. Co. KGaA.
Feng J.,University of Michigan |
Chen P.,Optimal Inc. |
Ni J.,University of Michigan
International Journal of Advanced Manufacturing Technology | Year: 2013
This study investigates grinding force prediction in microgrinding of ceramic materials by cohesive zone method (CZM) and finite element analysis (FEA). Based on detail abrasive cutting edge profile and maximum chip thickness analysis in microgrinding, a CZM-based finite element model is developed to predict grinding force in microgrinding of Alumina. The simulation result is compared with actual experimental measurement in different grinding conditions. The feasibility of force prediction in microgrinding of ceramic materials by CZM-based FEA is discussed and proven promising. © 2013 Springer-Verlag London.
University of Michigan and Optimal Inc. | Date: 2014-08-09
A reinforced composite panel and method of making the composite panel uses processed natural fibers such as bamboo along with a polymeric material. The method includes the steps of: treating a plant source comprising natural fibers with a solvent and processing the treated plant source. The processing step can include arranging the natural fibers into a sheet-like orientation in a variety of ways. A polymeric material is then applied to the natural fibers to form a composite sheet, and the composite panel can be formed from one or more composite sheets.
Dailly A.,General Motors |
Poirier E.,General Motors |
Poirier E.,Optimal Inc.
Energy and Environmental Science | Year: 2011
Exploring and evaluating on-board solid state hydrogen storage systems performance are of great interest for fuel cell electric vehicles development. In this report, we present gravimetric and volumetric capacities of a hydrogen storage system based on a densified MOF-177 adsorbent. This is, to our knowledge, the first thorough study of an engineered industrial scale MOFs for hydrogen storage application. The measurements were performed over the 50-120 K and 0-40 bar ranges, and modeled using micropore filling approaches. The performances of a potential 100 L vessel filled with the densified MOF-177 are inferred from the modeling parameters. A comparison of this technology with the 70 MPa compressed gas hydrogen system shows under which conditions the adsorbent offer advantages in terms of volumetric and gravimetric capacities. Further comparison with AX-21 activated carbon pellets reveals that densified MOF-177 stores about 40% more at 77 K and 35 bar. In order to get a physically sound modeling analysis, we introduced an approach to establish effective saturation pressures for supercritical adsorption. This approach insures a consistency between key model parameters and the observed liquid properties of the adsorbed phase at the lowest temperatures. We show that modeling using temperature-dependent saturation pressures and adsorbed phase densities leads to important differences in the projected usable storage capacities. Such differences can be as much as 25% at 50 K in the high pressure limit, revealing the importance of physical insights in the modeling approach. © 2011 The Royal Society of Chemistry.
Sheidaei A.,Michigan State University |
Xiao X.,Michigan State University |
Huang X.,General Motors |
Hitt J.,Optimal Inc
Journal of Power Sources | Year: 2011
The structural integrity of the separator is crucial to the abuse tolerance of a battery. To estimate its stress level in a battery, the mechanical property of the separator in situ in the battery environment must be known. This work investigated the tensile behavior of a single layer polypropylene (PP) separator in electrolyte solutions for Li-ion batteries using a dynamic mechanical analyzer (DMA). The measurements were carried out in both dry (ambient) and wet conditions for both the machine direction (MD) and the transverse direction (TD). In the wet condition, samples were submerged either in a DMC solvent or in a electrolyte solution of 1.1 M LiPF6 in EC/DMC (1/1 by volume). The DMA experiments were performed under uniaxial tension, creep, and frequency sweep modes. The results in all three modes demonstrated that the mechanical properties of the separator were significantly lower in wet conditions. For instance, in the MD, relative to the dry condition, the ratio of the Young's modulus was about 0.49 and 0.52 for DMC and 1.1 M LiPF6 in EC/DMC, respectively. The results indicate that the mechanical properties measured in dry condition using samples that had been preconditioned in solutions are not sufficient to represent the in situ material behavior. © 2011 Elsevier B.V. All rights reserved.
Shi X.,Optimal Inc. |
Cho J.Y.,Optimal Inc. |
Salvador J.R.,General Motors |
Yang J.,General Motors |
Wang H.,Oak Ridge National Laboratory
Applied Physics Letters | Year: 2010
High thermoelectric performance of a single crystal layered compound In4 Se3 was reported recently. We present here an electrical and thermal transport property study over a wide temperature range for polycrystalline samples of In4 Se3 and In4 Te3. Our data demonstrate that these materials are lightly doped semiconductors, leading to large thermopower and resistivity. Very low thermal conductivity, below 1 W/mK, is observed. The power factors for In4 Se3 and In4 Te3 are much smaller when compared with state-of-the-art thermoelectric materials. This combined with the very low thermal conductivity results in the maximum ZT value of less than 0.6 at 700 K for In4 Se3. © 2010 American Institute of Physics.
Beekman M.,University of South Florida |
Salvador J.,General Motors |
Shi X.,Optimal Inc. |
Nolas G.S.,University of South Florida |
Yang J.,General Motors
Journal of Alloys and Compounds | Year: 2010
Polycrystalline specimens of the delafossite oxide CuCoO2 (space group R over(3, ̄) m, a = 2.8494(2) Å, c = 16.926(1) Å, Z = 3) were prepared by metathesis reaction between CuCl and LiCoO2 at 590 °C and characterized by powder X-ray diffraction, thermal analysis, magnetic susceptibility, and electrical transport measurements. Decomposition of the title compound at 680 °C to its respective binary oxides was observed by thermal analysis. Electrical resistivity and magnetic susceptibility data for polycrystalline CuCoO2 are consistent with formal charge assignments of Cu+ and Co3+ for the transition metal constituents, while the room temperature Seebeck coefficient for the nominally undoped specimen was found to be -175 μV/K. The experimental data are consistent with recent density functional theory calculations for this material. © 2009 Elsevier B.V.
Mittal G.,University of Akron |
Raju M.P.,Optimal Inc. |
Bhari A.,University of Akron
Combustion and Flame | Year: 2011
Rapid compression machines (RCMs) typically incorporate creviced pistons to suppress the formation of the roll-up vortex. The use of a creviced piston, however, can enhance other multi-dimensional effects inside the RCM due to the crevice zone being at lower temperature than the main reaction chamber. In this work, such undesirable effects of a creviced piston are highlighted through computational fluid dynamics simulations of n-heptane ignition in RCM. Specifically, the results show that in an RCM with a creviced piston, additional flow of mass takes place from the main combustion chamber to the crevice zone during the first-stage of the two-stage ignition. This phenomenon is not captured by the zero-dimensional modeling approaches that are currently adopted. Consequently, a novel approach of 'crevice containment' is introduced and computationally evaluated in this paper. In order to avoid the undesirable effects of creviced piston, the crevice zone is separated from the main reaction chamber at the end of compression. The results with 'crevice containment' show significant improvement in the fidelity of zero-dimensional modeling in terms of predicting the overall ignition delay and pressure rise in the first-stage of ignition. Although the implementation of 'crevice containment' requires a modification in RCM design, in practice there are significant advantages to be gained through a reduction in the rate of pressure drop in the RCM combustion chamber and a quantitative improvement in the data obtained from the species sampling experiments. © 2011 The Combustion Institute.