East Hartford, CT, United States

UTRC - United Technologies Research Center

East Hartford, CT, United States

United Technologies Corporation is an American multinational conglomerate headquartered in the United Technologies Building in Hartford, Connecticut. It researches, develops, and manufactures high-technology products in numerous areas, including aircraft engines, helicopters, HVAC, fuel cells, elevators and escalators, fire and security, building systems, and industrial products, among others. UTC is also a large military contractor, producing missile systems and military helicopters, most notably the UH-60 Black Hawk helicopter. Gregory Hayes is the current CEO. Wikipedia.

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Sahai T.,UTRC - United Technologies Research Center | Speranzon A.,UTRC - United Technologies Research Center | Banaszuk A.,UTRC - United Technologies Research Center
Automatica | Year: 2012

We propose a novel distributed algorithm to cluster graphs. The algorithm recovers the solution obtained from spectral clustering without the need for expensive eigenvalue/eigenvector computations. We prove that, by propagating waves through the graph, a local fast Fourier transform yields the local component of every eigenvector of the Laplacian matrix, thus providing clustering information. For large graphs, the proposed algorithm is orders of magnitude faster than random walk based approaches. We prove the equivalence of the proposed algorithm to spectral clustering and derive convergence rates. We demonstrate the benefit of using this decentralized clustering algorithm for community detection in social graphs, accelerating distributed estimation in sensor networks and efficient computation of distributed multi-agent search strategies. © 2011 Elsevier Ltd. All rights reserved.

Erickson R.R.,UTRC - United Technologies Research Center | Soteriou M.C.,UTRC - United Technologies Research Center
Combustion and Flame | Year: 2011

The impact of increased reactant temperature on the dynamics of bluff-body stabilized premixed flows is investigated using numerical simulation. A two-dimensional triangular bluff body is considered. Flow compressibility is assumed to exist at the low Mach number limit and combustion is fast and robust such that a flamesheet representation is assumed to apply. In this formulation, reactant temperature variations are represented via corresponding temperature ratio and flame speed variations. The Lagrangian, Transport Element Method is used to provide the numerical solutions. Results indicate that as reactant temperature increases, the fluid dynamics transition from a low amplitude, broadband, coarsely symmetric (about the bluff-body centerline) behavior, to a high amplitude, tonal and asymmetric one that bears similarities to the corresponding non-reacting flow. The reasons for this are that as the reactant temperature increases, (i) the temperature ratio across the flame is reduced, thus reducing combustion exothermicity, and (ii) the flame speed increases causing the flame to propagate away from the bluff-body wake. In both cases the ability of the two main combustion-driven fluid dynamical processes, namely volumetric expansion and baroclinic generation to impact the bluff body generated vorticity is reduced. Reduction in baroclinic generation enables to wake to survive futher downsteam and makes the flow susceptible to the wake instability. As reactant temperature is increased the location of the onset of the instability moves upstream. At very high reactant temperatures even the near field symmetrizing effect of volumetric expansion is overwhelmed and asymmetric vortex shedding is witnessed at the bluff body. Even in this regime, the flow differs from the non-reacting flow in that it is susceptible to bifurcations in vortex shedding behavior that are linked to local flame-vortex interactions. Results also show that in the general case, knowledge of the fluid dynamics alone is not sufficient to characterize the flame dynamics, as the flame position in relation to the vorticity field is critical to the unsteady flame response. Specifically, the flame exhibits a similar transition from a broadband to a tonal response but the amplitude is not monotonically increasing. Rather it experiences a regime of decreasing response for intermediate reactant temperatures where the flame propagation away from the wake appears to dominate the increase in fluid dynamical induced oscillations due to the enhancement of the asymmetric mode. © 2011.

Abbaszadeh M.,UTRC - United Technologies Research Center | Marquez H.J.,University of Alberta
Automatica | Year: 2012

In this paper, a generalized robust nonlinear H ∞ filtering method is proposed for a class of Lipschitz descriptor systems, in which the nonlinearities appear both in the state and measured output equations. The system is assumed to have norm-bounded uncertainties in the realization matrices as well as nonlinear uncertainties. We synthesize the H ∞ filter through semidefinite programming and strict LMIs. The admissible Lipschitz constants of the nonlinear functions are maximized through LMI optimization. The resulting H ∞ filter guarantees asymptotic stability of the estimation error dynamics with prespecified disturbance attenuation level and is robust against time-varying parametric uncertainties as well as Lipschitz nonlinear additive uncertainty. Explicit bound on the tolerable nonlinear uncertainty is derived based on a norm-wise robustness analysis. © 2012 Elsevier Ltd. All rights reserved.

Shao M.,UTC Power | Peles A.,UTRC - United Technologies Research Center | Shoemaker K.,UTC Power
Nano Letters | Year: 2011

We determined the size-dependent specific and mass activities of the oxygen reduction in HClO4 solutions on the Pt particles in the range of 1-5 nm. The maximal mass activity at 2.2 nm is well explained based on density functional theory calculations performed on fully relaxed nanoparticles. The presence of the edge sites is the main reason for the low specific activity in nanoparticles due to very strong oxygen binding energies at these sites. Our results clearly demonstrate that the catalytic activity highly depends on the shape and size of the nanoparticles. © 2011 American Chemical Society.

Khalil Y.F.,UTRC - United Technologies Research Center
Journal of Loss Prevention in the Process Industries | Year: 2013

This paper discusses the results of an experimental program carried out to determine dust cloud deflagration parameters of selected solid-state hydrogen storage materials, including complex metal hydrides (sodium alanate and lithium borohydride/magnesium hydride mixture), chemical hydrides (alane and ammonia borane) and activated carbon (Maxsorb, AX-21). The measured parameters include maximum deflagration pressure rise, maximum rate of pressure rise, minimum ignition temperature, minimum ignition energy and minimum explosible concentration. The calculated explosion indexes include volume-normalized maximum rate of pressure rise (KSt), explosion severity (ES) and ignition sensitivity (IS). The deflagration parameters of Pittsburgh seam coal dust and Lycopodium spores (reference materials) are also measured. The results show that activated carbon is the safest hydrogen storage media among the examined materials. Ammonia borane is unsafe to use because of the high explosibility of its dust. The core insights of this contribution are useful for quantifying the risks associated with use of these materials for on-board systems in light-duty fuel cell-powered vehicles and for supporting the development of hydrogen safety codes and standards. These insights are also critical for designing adequate safety features such as explosion relief venting and isolation devices and for supplementing missing data in materials safety data sheets. © 2012 Elsevier Ltd.

Khalil Y.F.,UTRC - United Technologies Research Center
Journal of Loss Prevention in the Process Industries | Year: 2013

This paper aims to develop quantitative insights based on measured deflagration parameters of hybrid mixtures of activated carbon (AC) dust and hydrogen (H2) gas in air. The generated experimental evidence is used to reject the claim of the null hypothesis (H0) that severity of deflagrations of H2/air mixtures always bound the severity of deflagrations of heterogenous combustible mixtures of AC dust/H2/air containing the same H2 concentrations as in the H2/air binaries. The core insights of this investigation show that the maximum deflagration pressure rise (ΔPMAX) and maximum rate of pressure rise ((dP/dt)MAX) of this hybrid mixture are greater than those corresponding to deflagrations of H2/air mixtures for all the dust and H2 concentrations being examined. The deflagration severity indices (KSt and ES) of the hybrid mixture containing 29 mol% H2 are found to be greater than those of the H2/air mixture containing 29 mol% H2. Also, the minimum explosible concentration (MEC) of the hybrid mixture is lower than that of the AC dust in air only. The insights gained should lead to better realization of the severity of a postulated safety-significant accident scenario associated with on-board cryoadsorption H2 storage systems for fuel-cell (FC) powered light-duty vehicles. The identified insights could also be relevant to other industrial processes where combustible dusts are generated in the vicinity of solvent vapors. Moreover, these insights should be useful for supporting quantitative risk assessment (QRA) of on-board H2 storage systems, designing improved safety measures for cryoadsorption H2 storage tanks, and guiding H2 safety standards and transportation regulations. © 2013 Elsevier Ltd.

Dwari S.,UTRC - United Technologies Research Center | Parsa L.,Rensselaer Polytechnic Institute
IEEE Transactions on Industrial Electronics | Year: 2011

This paper presents fault-tolerant control techniques for five-phase permanent-magnet motors with trapezoidal back electromotive forces under various open-circuit conditions. The proposed fault-tolerant control methods use only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The control techniques are developed by applying a concept that correlates the currents in the healthy phases based on their symmetry in space with respect to the fault in a machine. Optimum solutions under the single-phase open-circuit fault condition and double-phase open-circuit fault conditions are presented. The presented solutions are derived to increase the average output torque while reducing the torque pulsations and satisfying the zero-neutral-current constraint. Detailed experimental results are presented for the verification of the proposed solutions. © 2011 IEEE.

Krishnamurthy S.,UTRC - United Technologies Research Center
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2012

The paper presents a half-bridge topology for an AC-AC electronic transformer. The primary motivation for an electronic transformer is to reduce the weight of the magnetics needed for isolating low frequency (50-60Hz) AC lines. The half bridge electronic transformer topology achieves the needed isolation with high frequency magnetics and without the need for an intermediary DC link. The absence of the DC link reduces the number of intermediate steps and hence the topology has the potential for overall higher efficiency. The paper discusses the operation of the topology and presents simulation and preliminary experimental results. © 2012 IEEE.

Jiang D.,UTRC - United Technologies Research Center | Wang F.F.,University of Tennessee at Knoxville
IEEE Transactions on Power Electronics | Year: 2013

Compared with the widely used constant switching frequency pulse-width-modulation (PWM) method, variable switching frequency PWM can benefit more because of the extra freedom. Based on the analytical expression of current ripple of three-phase converters, variable switching frequency control methods are proposed to satisfy different ripple requirements. Switching cycle Ts is updated in DSP in every interruption period based on the ripple requirement. Two methods are discussed in this paper. The first method is designed to arrange the current ripple peak value within a certain value and can reduce the equivalent switching frequency and electromagnetic interference (EMI) noise; the second method is designed to keep ripple current RMS value constant and reduce the EMI noise. Simulation and experimental results show that variable switching frequency control could improve the performance of EMI and efficiency without impairing the power quality. © 1986-2012 IEEE.

Cai C.,UTRC - United Technologies Research Center | Hagen G.,UTRC - United Technologies Research Center
IEEE Transactions on Automatic Control | Year: 2010

For a string of (possibly arbitrarily many) coupled stable subsystems that are equipped with a dynamic property of negative imaginary frequency response, we characterize stability of the string by a dc gain condition that can be expressed as a continued fraction with verifiable convergence properties. Through analysis of the convergence of the continued fraction, we establish stability results for the string with various coupling gains and patterns. The derived results are applied to locally decentralized control of large vehicle platoons, possibly with heterogenous neighboring coupling. © 2010 IEEE.

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