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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.

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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