Ford Motor Company (Czechia)

Widespread adoption of hydrogen as a vehicular fuel depends critically upon the ability to store hydrogen on-board at high volumetric and gravimetric densities, as well as on the ability to extract/insert it at sufficiently rapid rates. As current storage methods based on physical means--high-pressure gas or (cryogenic) liquefaction--are unlikely to satisfy targets for performance and cost, a global research effort focusing on the development of chemical means for storing hydrogen in condensed phases has recently emerged. At present, no known material exhibits a combination of properties that would enable high-volume automotive applications. Thus new materials with improved performance, or new approaches to the synthesis and/or processing of existing materials, are highly desirable. In this critical review we provide a practical introduction to the field of hydrogen storage materials research, with an emphasis on (i) the properties necessary for a viable storage material, (ii) the computational and experimental techniques commonly employed in determining these attributes, and (iii) the classes of materials being pursued as candidate storage compounds. Starting from the general requirements of a fuel cell vehicle, we summarize how these requirements translate into desired characteristics for the hydrogen storage material. Key amongst these are: (a) high gravimetric and volumetric hydrogen density, (b) thermodynamics that allow for reversible hydrogen uptake/release under near-ambient conditions, and (c) fast reaction kinetics. To further illustrate these attributes, the four major classes of candidate storage materials--conventional metal hydrides, chemical hydrides, complex hydrides, and sorbent systems--are introduced and their respective performance and prospects for improvement in each of these areas is discussed. Finally, we review the most valuable experimental and computational techniques for determining these attributes, highlighting how an approach that couples computational modeling with experiments can significantly accelerate the discovery of novel storage materials (155 references).

An adaptive output feedback control scheme for the output tracking of a class of continuous-time nonlinear plants is presented. An RBF neural network is used to adaptively compensate for the plant nonlinearities. The network weights are adapted using a Lyapunov-based design. The method uses parameter projection, control saturation, and a high-gain observer to achieve semi-global uniform ultimate boundedness. The effectiveness of the proposed method is demonstrated through simulations. The simulations also show that by using adaptive control in conjunction with robust control, it is possible to tolerate larger approximation errors resulting from the use of lower order networks.

Although the potential of the powerful mapping and representational capabilities of recurrent network architectures is generally recognized by the neural network research community, recurrent neural networks have not been widely used for the control of nonlinear dynamical systems, possibly due to the relative ineffectiveness of simple gradient descent training algorithms. Developments in the use of parameter-based extended Kalman filter algorithms for training recurrent networks may provide a mechanism by which these architectures will prove to be of practical value. This paper presents a decoupled extended Kalman filter (DEKF) algorithm for training of recurrent networks with special emphasis on application to control problems. We demonstrate in simulation the application of the DEKF algorithm to a series of example control problems ranging from the well-known cart-pole and bioreactor benchmark problems to an automotive subsystem, engine idle speed control. These simulations suggest that recurrent controller networks trained by Kalman filter methods can combine the traditional features of state-space controllers and observers in a homogeneous architecture for nonlinear dynamical systems, while simultaneously exhibiting less sensitivity than do purely feedforward controller networks to changes in plant parameters and measurement noise.

Abstract In the mid‐1970s, it was recognized that chlorofluorocarbons (CFCs) were strong greenhouse gases that could have substantial impacts on radiative forcing of climate change, as well as being substances that deplete stratospheric ozone. Around a decade later, this group of radiatively active compounds was expanded to include a large number of replacements for ozone‐depleting substances such as chlorocarbons, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), bromofluorocarbons, and bromochlorofluorocarbons. This paper systematically reviews the published literature concerning the radiative efficiencies (REs) of CFCs, bromofluorocarbons and bromochlorofluorocarbons (halons), HCFCs, HFCs, PFCs, sulfur hexafluoride, nitrogen trifluoride, and related halogen containing compounds. In addition, we provide a comprehensive and self‐consistent set of new calculations of REs and global warming potentials (GWPs) for these compounds, mostly employing atmospheric lifetimes taken from the available literature. We also present global temperature change potentials for selected gases. Infrared absorption spectra used in the RE calculations were taken from databases and individual studies and from experimental and ab initio computational studies. Evaluations of REs and GWPs are presented for more than 200 compounds. Our calculations yield REs significantly (> 5%) different from those in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) for 49 compounds. We present new RE values for more than 100 gases which were not included in AR4. A widely used simple method to calculate REs and GWPs from absorption spectra and atmospheric lifetimes is assessed and updated. This is the most comprehensive review of the radiative efficiencies and global warming potentials of halogenated compounds performed to date.

A host of fascinating and useful magnetic phenomena are found in composites containing magnetizable particles in viscoelastic solids. Embedding magnetically soft iron particles in natural rubber produces a class of magnetostrictive composites sometimes termed magnetorheological (MR) elastomers. We have previously shown that these materials can exhibit viscoelastic moduli that increase substantially in an applied magnetic field. In this paper, we incorporate MR elastomers in a simple resonant structure called a tuned absorber to measure the complex dynamic shear moduli of these materials at high frequencies. We find that the fluid-induced modulus increase in MR elastomers is substantial even at kilohertz mechanical frequencies. As in previous measurements at low frequencies, the moduli are generally found to decrease with strain amplitude. We also report preliminary measurements of the relatively large elongation of these materials in applied magnetic fields.

Abstract A new formulation of the element‐free Galerkin (EFG) method is presented in this paper. EFG has been extensively popularized in the literature in recent years due to its flexibility and high convergence rate in solving boundary value problems. However, accurate imposition of essential boundary conditions in the EFG method often presents difficulties because the Kronecker delta property, which is satisfied by finite element shape functions, does not necessarily hold for the EFG shape function. The proposed new formulation of EFG eliminates this shortcoming through the moving kriging (MK) interpolation. Two major properties of the MK interpolation: the Kronecker delta property ( ϕ I ( s J )= δ IJ ) and the consistency property (∑ I n ϕ I ( x )=1 and ∑ I n ϕ I ( x ) x Ii = x i ) are proved. Some preliminary numerical results are given. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract Additive manufacturing, i.e., 3D printing, is being increasingly utilized to fabricate a variety of complex‐shaped electronics and energy devices (e.g., batteries, supercapacitors, and solar cells) due to its excellent process flexibility, good geometry controllability, as well as cost and material waste reduction. In this review, the recent advances in 3D printing of emerging batteries are emphasized and discussed. The recent progress in fabricating 3D‐printed batteries through the major 3D‐printing methods, including lithography‐based 3D printing, template‐assisted electrodeposition‐based 3D printing, inkjet printing, direct ink writing, fused deposition modeling, and aerosol jet printing, are first summarized. Then, the significant achievements made in the development and printing of battery electrodes and electrolytes are highlighted. Finally, major challenges are discussed and potential research frontiers in developing 3D‐printed batteries are proposed. It is expected that with the continuous development of printing techniques and materials, 3D‐printed batteries with long‐term durability, favorable safety as well as high energy and power density will eventually be widely used in many fields.

Integral control of large-scale systems implies coordination of activities by information exchange via communication networks. Usually these networks are shared with other users. Thus traffic conditions in the network may introduce time-varying random delays in the control loop with adverse effects on its performance and stability. Hence, the control must be designed to compensate for these delays. Recent work in modelling integrated control and communication systems has shown that the communication specific phenomena inducing random communication delays (such as multirate sampling, vacant sampling and message rejection) may be encompassed by finite-dimensional linear discrete-time models, provided that the plant and the controller are linear and time invariant. Existing approaches to the design of integrated control systems rely on conservative stability tests, because only sufficient stability conditions were found for systems with random time-varying delays. In this paper, necessary and sufficient conditions are found for zero-state mean-square exponential stability of the considered class of control systems. Numerical tests for zero-state stability are outlined and illustrated by a simple example. Finally, the results are also demonstrated on specific hardware, a multiprocessor real-time control network which has been recently developed.

Abstract Human activity has led to increased atmospheric concentrations of many gases, including halocarbons, and may lead to emissions of many more gases. Many of these gases are, on a per molecule basis, powerful greenhouse gases, although at present‐day concentrations their climate effect is in the so‐called weak limit (i.e., their effect scales linearly with concentration). We published a comprehensive review of the radiative efficiencies (RE) and global warming potentials (GWP) for around 200 such compounds in 2013 (Hodnebrog et al., 2013, https://doi.org/10.1002/rog.20013 ). Here we present updated RE and GWP values for compounds where experimental infrared absorption spectra are available. Updated numbers are based on a revised “Pinnock curve”, which gives RE as a function of wave number, and now also accounts for stratospheric temperature adjustment (Shine & Myhre, 2020, https://doi.org/10.1029/2019MS001951 ). Further updates include the implementation of around 500 absorption spectra additional to those in the 2013 review and new atmospheric lifetimes from the literature (mainly from WMO (2019)). In total, values for 60 of the compounds previously assessed are based on additional absorption spectra, and 42 compounds have REs which differ by >10% from our previous assessment. New RE calculations are presented for more than 400 compounds in addition to the previously assessed compounds, and GWP calculations are presented for a total of around 250 compounds. Present‐day radiative forcing due to halocarbons and other weak absorbers is 0.38 [0.33–0.43] W m −2 , compared to 0.36 [0.32–0.40] W m −2 in IPCC AR5 (Myhre et al., 2013, https://doi.org/10.1017/CBO9781107415324.018 ), which is about 18% of the current CO 2 forcing.

Abstract. This article, the seventh in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas-phase and photochemical reactions related to Criegee intermediates previously published in Atmospheric Chemistry and Physics (ACP) in 2006 and implemented on the IUPAC website up to 2020. The article consists of an introduction, description of laboratory measurements, a discussion of rate coefficients for reactions of O3 with alkenes producing Criegee intermediates, rate coefficients of unimolecular and bimolecular reactions and photochemical data for reactions of Criegee intermediates, and an overview of the atmospheric chemistry of Criegee intermediates. Summary tables of the recommended kinetic and mechanistic parameters for the evaluated reactions are provided. Data sheets summarizing information upon which the recommendations are based are given in two files, provided as a Supplement to this article.

Results of stationary and transient response analyses of the Golden Gate suspension bridge, and the New River Gorge and Cold Spring Canyon deck arch bridges, to a general spatially varying earthquake ground motion (SVEGM) model are presented. The results are compared with responses computed using identical and delayed excitations. The use of identical excitations is in general unacceptable for these long-span bridges, and the use of delayed excitations is acceptable only for the longitudinal response of short arch bridges. Surprisingly, the transient lateral displacements of the suspension bridge center span significantly overshoot the corresponding stationary displacements for the filtered Kanai-Tajami excitation power spectrum; this spectrum may therefore be unsuitable for analyzing very flexible structures. The qualitative effects of SVEGM on stationary and transient force responses are found to be similar.

We detected a compound previously unreported in the atmosphere, trifluoromethyl sulfur pentafluoride (SF(5)CF(3)). Measurements of its infrared absorption cross section show SF(5)CF(3) to have a radiative forcing of 0.57 watt per square meter per parts per billion. This is the largest radiative forcing, on a per molecule basis, of any gas found in the atmosphere to date. Antarctic firn measurements show it to have grown from near zero in the late 1960s to about 0.12 part per trillion in 1999. It is presently growing by about 0.008 part per trillion per year, or 6% per year. Stratospheric profiles of SF(5)CF(3) suggest that it is long-lived in the atmosphere (on the order of 1000 years).

Abstract Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001 KEY WORDS: Boundary FrictionEnergy ConservationFriction Modifier Additives Notes Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001

Greater than the sum of its parts: Hydrogen storage in complex hydrides is accelerated by using the ternary composite 2 LiNH2/LiBH4/MgH2, which exhibits a “self-catalyzing” reaction pathway that results in faster H2 desorption, lower desorption temperatures, and suppression of NH3 release in comparison to the constituent binary composites (see diagram). The enhanced properties arise from the incorporation of an ionic liquid phase (Li4BH3H10) and from ancillary-reaction seeding of a reversible H2 storage reaction. Conventional (e.g. MgH2) and complex hydrides (e.g. alanates, borohydrides, and amides) are the two primary classes of solid-state hydrogen-storage materials.1–3 Many of these “high-density” hydrides have the potential to store large amounts of hydrogen by weight (up to 18.5 wt % for LiBH4) and/or volume (up to 112 g L−1 for MgH2), values that are comparable to the hydrogen content of gasoline (15.8 wt %, 112 g L−1). However, all known hydrides are inadequate for mobile storage applications due to one or more of the following limitations: a) unfavorable thermodynamics (they require high temperatures to release hydrogen4), b) poor kinetics (low rates of hydrogen release and uptake), c) decomposition pathways involving the release of undesirable by-products (e.g. ammonia), and/or d) an inability to reabsorb hydrogen at modest temperatures and pressures (i.e. “irreversibility”). In spite of these drawbacks, renewed interest in complex hydrides has been stimulated recently by substantial improvements in their kinetics and reversibility5, 6 provided by catalytic doping (e.g. TiCl3-doped NaAlH4),7, 8 and by thermodynamic enhancements achieved through reactive binary mixtures9 such as LiNH2/MgH2,10, 11 LiBH4/MgH2,12 and LiNH2/LiBH4.13, 14 These compositions, previously termed “reactive hydride composites”,15 represent the state-of-the-art in hydrogen-storage materials; compared to their constituent compounds, they exhibit improved thermodynamic properties, higher hydrogen purity, and, in some cases, reversibility. The desorption behavior of these previously studied composites is illustrated in Figure 1 a. It is evident from the hydrogen desorption profile (top panel) that the composites generally desorb hydrogen at significantly lower temperatures than their individual components. For example, the lowest temperature reaction, which involves a 2:1 mixture of LiNH2 and MgH2, has a desorption temperature more than 100 °C lower than that of either MgH2 (approx. 350 °C) or LiNH2 (which releases only NH3) alone. Although these binary reactions present significant benefits, they all have well-known disadvantages: a) their lowered desorption temperatures are still too high, b) the reaction involving LiNH2 and LiBH4 is irreversible, c) the nitrogen-containing binaries LiNH2/MgH2 and LiNH2/LiBH4 emit a significant amount of ammonia (a proton-exchange membrane fuel cell (PEM-FC) poison) together with the hydrogen (Figure 1 a, bottom panel), and, most significantly, d) hydrogen desorption/uptake in all of these binary composites is too slow. Therefore, further improvement in these areas is highly desirable. a) Hydrogen (top) and ammonia (bottom) kinetic desorption data as a function of temperature (5 °C min−1 to 550 °C) for the ternary composition (blue trace) and its unary and binary constituents. Hydrogen desorption is measured in weight percent (wt %) to 1 bar whereas relative ammonia release is measured as partial pressure (torr) in a flow-through set-up (100 sccm Ar). b) Ternary phase space defined by unary compounds (nodes), LiBH4 (pink), MgH2 (purple), and LiNH2 (orange) and the binary mixtures (edges), LiBH4/MgH2 (gray), MgH2/LiNH2 (green), and LiNH2/LiBH4 (red). The present ternary composition, which is a 2:1:1 mixture of LiNH2, LiBH4, and MgH2, and previously investigated binaries, are identified. Herein we present a strategy for enhancing the properties of binary composites through the creation of a multi-component composite of three hydride compounds (2 LiNH2/LiBH4/MgH2). The improved properties of this system arise almost entirely from a “self-catalyzing” reaction pathway that results in faster kinetics and lower desorption temperatures than for the binary composites and almost complete suppression of ammonia release. The key elements that contribute to the enhanced properties are the incorporation of a low melting temperature ionic liquid (Li4BH3H10) and a mechanism for seeding the products of a reversible hydrogen desorption reaction.16 The choice of the 2 LiNH2/LiBH4/MgH2 stoichiometry is based on several factors: a) the constituent hydrides all possess high gravimetric/volumetric capacities, b) binary mixtures of these hydrides are among the best known hydrogen-storage materials (see Figure 1 a, top panel), c) mixtures containing MgH2 are known to suppress ammonia release from nitrogen-containing hydrides such as LiNH2 (Figure 1 a, bottom panel), and d) a stable, lightweight compound, namely lithium magnesium boron nitride (LiMgBN2), which contains N, B, and Mg in a 2:1:1 ratio (the same as our stoichiometric composite), is known which could serve as a potential dehydrogenated product phase. The compositional phase space of the ternary composite is shown in the Gibbs triangle in Figure 1 b and information regarding the sample synthesis and preparation conditions is given in the Experimental Section. We begin our discussion of this system by summarizing its principal hydrogen-storage attributes in relation to those of the unary and binary components. Employing a wide range of experimental phase analyses and first-principles evaluation of reaction thermodynamics, we subsequently identify a complex, “cascading” sequence of reactions that explain the observed properties. We conclude with a more detailed discussion of the proposed “self-catalyzing” mechanism. Lowered desorption temperatures: The measured kinetic desorption behavior (5 °C min−1, 1 bar) of the ternary composite is compared with the constituent unary and binary components in the upper panel of Figure 1 a. The ternary system rapidly releases hydrogen in a process that begins at 150 °C (top panel), which is about 50–200 °C lower than the binary composites, thereby indicating significantly improved kinetics and/or thermodynamics. The total capacity of the ternary composite is 8.2 wt %. Improved hydrogen purity: The composition of the gas released from the ternary composite while heating at 5 °C min−1 in a flow of 100 sccm argon is plotted in comparison with the binary composites in the lower panel of Figure 1 a. The ammonia released by the ternary composite is less than the 100 ppm detection limit of our instrument; the ammonia released from the nitrogen-containing binaries was found to be more than an order of magnitude larger. No other volatile boron- and/or nitrogen-containing by-products were detected throughout the desorption process. Reversibility: The reversible storage capacity and response to cycling were determined from a series of charge/discharge experiments performed with a Sievert-type PCT apparatus at 160 °C and charging (discharging) at 100 (1) bar. The results for five charge/discharge cycles (Figure 2 a) show that the as-prepared material rapidly releases approximately 3.0 wt % of hydrogen within 20 minutes. After recharging, the second through fifth desorption cycles consistently liberate around 2.8 wt % of hydrogen, a reversible capacity at moderate temperature that is among the best for solid-state hydrogen storage.5–8 a) Hydrogen desorption kinetics at 160 °C and 1 bar over five cycles after subsequent charging (160 °C and 100 bar hydrogen). b) Reversible isothermal kinetic hydrogen desorption data (to 1 bar) for the ternary composition based on the second desorption cycle at 140 (•), 150 (▾), 160 (□), and 180 °C (⧫) versus time. Kinetics: The reversible isothermal kinetic desorption profiles for the second desorption cycle (to 1 bar) were collected at 140, 150, 160, and 180 °C (Figure 2 b). The ternary composite is capable of desorbing more than 2.5 wt % hydrogen in times ranging from 10 min (180 °C) to 2.5 h (140 °C) in this temperature range. The remaining hydrogen is liberated in a second step at higher temperatures for a total hydrogen capacity of 8.2 wt % (Figure 3). The initial release of hydrogen at both 260 and 320 °C is dramatically accelerated, with 3.2 wt % released within minutes, while the subsequent desorption steps are more influenced by temperature, reaching full desorption after 1.5 and 14 h at 320 and 260 °C, respectively. Isothermal kinetic hydrogen desorption to 1 bar for the ternary composition at 260 and 320 °C versus time. The unique desorption behavior described above strongly suggests that the reaction mechanism(s) of the ternary composite is not a simple superposition of the known binary reactions. To understand its hydrogen-release characteristics, we therefore collected temperature-programmed-desorption mass spectrometry (TPD-MS) data at a constant heating rate and carrier gas flow (5 °C min−1, 100 sccm argon flow; Figure 4 a). Four distinct hydrogen-release events occur (maxima at 180, 190 (shoulder), 310, and 560 °C, respectively), with an initial desorption onset at 110 °C.17 TPD-MS data were also collected for the cycled/recharged material (See Supporting Information). These data clearly show that the first steep desorption step (at 180 °C) in the as-prepared sample is no longer observed in the recharged sample. Instead, the peak temperature for the recharged sample is now shifted to the shoulder region for the fresh material (approx. 190 °C), thus indicating that the reaction corresponding to the shoulder is reversible, which is consistent with the powder X-ray diffraction (PXRD) and IR spectroscopic analyses (discussed below). a) TPD-MS data for the ternary composition depicting hydrogen (m/z 2, blue) and ammonia (m/z 17, pink) as a function of temperature (heating at 5 °C min−1 to 575 °C). b) Phase composition as a function of desorbed hydrogen amount (wt %) and temperature (°C) as determined from the static PXRD and IR data. Phase identification: Phase-composition studies were carried out for identically prepared samples, which were desorbed to varying degrees at 1 bar hydrogen by heating at 5 °C min−1 in a water displacement apparatus (see Supporting Information) to identify the species involved in the various desorption reactions. Following desorption, each sample was quenched and analyzed by PXRD and IR spectroscopy. The results are summarized in Figure 4 b, and raw data and phase assignments are provided as Supporting Information. The as-prepared sample (ball milling 2 g of LiNH2, LiBH4, and MgH2 in a 2:1:1 ratio for 5 h) contains two new species (Mg(NH2)2 and Li4BN3H10) and no residual LiNH2, which is indicative of milling-induced transformations. Residual MgH2 and LiBH4 starting materials are also present. Growth of Mg(NH2)2 and (weakly crystalline) LiH is detected upon initial heating to 140 °C before any appreciable amount of hydrogen is released. At the same time, the diffraction peaks for Li4BN3H10 disappear. As the characteristic symmetric and asymmetric amide NH IR frequencies (observed: 3301 and 3242 cm−1; literature:18 3303 and 3243 cm−1) persist, we conclude that Li4BN3H10 has melted. Further heating to 180 °C results in the release of 2.0 wt % hydrogen (first low temperature event in Figure 4 a) and the formation of Li2Mg(NH)2, based on its three characteristic peaks at 30.7°, 51.3°, and 60.9° in the PXRD pattern19 and the signature NH stretch in the IR spectrum (observed: 3178 cm−1; literature:20 3187 cm−1). This phase continues to grow in intensity until 255 °C, at which point 4.0 wt % H2 has desorbed. At this stage, MgH2 and Mg(NH2)2 have been completely consumed while Li4BN3H10 is significantly depleted. The second major hydrogen releasing event occurs between 255 and 375 °C and corresponds to a total of 8.2 wt % desorbed hydrogen. Li2Mg(NH)2 and LiBH4 are consumed during this stage and Mg3N2 and Li3BN2 are formed. Trace amounts of LiH and an unknown phase (denoted as “Phase X”) are also detected by PXRD.21 Further heating to 500 °C does not produce additional hydrogen but rather an observed phase transformation consistent with the consumption of Li3BN2, Mg3N2, and LiBH4 and the production of LiH and LiMgBN2.22 The final hydrogen releasing step (>500 °C) is attributed to decomposition of LiH (third major event in Figure 4 a). Variable-temperature in situ PXRD was used to validate the above phase assignments and to provide phase transformation information (see the Supporting Information for instrument set-up and data collection protocol). Figure 5 a shows the raw PXRD data as a function of temperature (25–450 °C) and Figure 5 b shows the two-dimensional contour plot. The phase assemblage as a function of temperature is shown in Figure 5 c. The data reveal that the sequence and relative phase contributions are identical to those observed by static PXRD, thereby confirming the proposed reaction sequence. Furthermore, the in situ data reveal that the Li4BN3H10 and MgH2 phases disappear rapidly (by 100 and 150 °C, respectively) during initial heating of the as-prepared material and prior to any hydrogen release. The observed melting of Li4BN3H10 at 100 °C occurs at a significantly lower temperature than previously reported (150 °C).23 This low temperature melt may serve as an effective mass transfer medium or homogenizing agent and aid in the distribution of Li2Mg(NH)2 (produced in the first desorption step reaction between Li4BN3H10 and MgH2), which would in turn serve as Li2Mg(NH)2 nucleation seeds for a second step reaction between Mg(NH2)2 and LiH. The presence of the ionic liquid may therefore positively influence the desorption kinetics of the initial hydrogen release reactions. a) Raw PXRD data for the ternary composition as a function of temperature (25–450 °C). b) The corresponding two-dimensional contour plot derived from the raw patterns in (a). c) Plot of the relative amounts of individual phases as a function of temperature. Reaction pathway: A set of proposed reactions are summarized in Figure 6. Our assignment of reactions takes into account the observed and theoretical hydrogen capacity for each step, the reversible amount of stored hydrogen, and the phase compositions (obtained from both quenched/static and in situ PXRD and IR spectroscopy). A reaction scheme flowchart is included in the Supporting Information. The TPD-MS curve from Figure 4 a is incorporated to indicate the temperature region under which each reaction occurs. The reaction enthalpies (ΔHcalcd) and free energies (ΔGcalcd) at 300 K obtained by density functional theory calculations are also included in this table. The fact that all the calculated free energies are negative suggests that the proposed reactions are thermodynamically reasonable. (The activation energies for reactions (2) and (4) are given as Supporting Information.) Proposed reaction pathway for the ternary composite, including the observed/theoretical hydrogen capacity, reaction enthalpy (ΔH), free energy (ΔG) (both in kJ mol−1 for products at 300 K), and the corresponding temperature range (coupled to the TPD-MS curve). The reaction numbers in this figure correspond to those used in the text. We refer to the ternary composite as “self-catalyzed” in the sense that one reaction [reaction (2)] pre-forms the product nuclei (Li2Mg(NH)2) for the subsequent reaction [reaction (3)], which results in an enhancement of the overall kinetic properties. A separate study has confirmed the beneficial effects of product seeding in improving the desorption kinetics of the Mg(NH2)2/LiH system.24 It should be emphasized that the thermodynamics of the binary reaction between Mg(NH2)2 and LiH [reaction (3)] indicate that it should proceed at a lower temperature than observed. Our results suggest a new rational route by which the kinetic properties of existing hydrogen-desorption reactions can be enhanced, namely by coupled self-catalyzing reactions. In conclusion, our study of the ternary LiBH4/2 LiNH2/MgH2 composite has led to the discovery of a new “self-catalyzing” strategy for enhancing the kinetics of hydrogen storage in complex hydride composites. We have demonstrated through a wide-ranging experimental and first-principle computational analysis that this self-catalyzing mechanism arises from a set of coupled, ancillary reactions that yield both a homogenizing ionic liquid phase and product nuclei for a subsequent reversible hydrogen-storage reaction. These effects combine to yield enhanced low-temperature desorption kinetics and a significant reduction in ammonia liberation relative to the state-of-the-art binary constituent composites. The strategy of utilizing built-in, ancillary reactions to catalyze a primary hydrogen-storage reaction suggests prospective routes for advancing existing and future storage materials. Sample Preparation: LiNH2 (95 % purity, Sigma-Aldrich), MgH2 (95 % purity, Gelest), and LiBH4 (95 % purity, Sigma-Aldrich) were used as received. All sample handling was performed in an MBraun Labmaster 130 glove box maintained under argon with less than 0.1 ppm O2 and H2O vapor. The binary composites 2 LiNH2/LiBH4, 2 LiNH2/MgH2, and 2 LiBH4/MgH2 were prepared according to literature protocols.10, 12, 13 For the ternary composite, two grams of LiNH2, LiBH4, and MgH2 in a 2:1:1 molar ratio was loaded into a milling vial containing three stainless steel balls weighing 8.4 g each. Mechanical milling was carried out using a Spex 8000 high-energy mixer/mill for 1–20 h. Characterization and Property Evaluation: All methods relating to sample characterization and property evaluation, including powder X-ray diffraction (PXRD), IR spectroscopy, kinetic hydrogen desorption/absorption studies (PCT, TPD-MS, and WDD), density functional theory (DFT) calculations, and activation energy calculations are described in detail in the Supporting Information. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z703756_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Metal-organic frameworks (MOFs) are an emerging class of microporous, crystalline materials with potential applications in the capture, storage, and separation of gases. Of the many known MOFs, MOF-5 has attracted considerable attention because of its ability to store gaseous fuels at low pressure with high densities. Nevertheless, MOF-5 and several other MOFs exhibit limited stability upon exposure to reactive species such as water. The present study quantifies the impact of humid air exposure on the properties of MOF-5 as a function of exposure time, humidity level, and morphology (i.e., powders vs pellets). Properties examined include hydrogen storage capacity, surface area, and crystallinity. Water adsorption/desorption isotherms are measured using a gravimetric technique; the first uptake exhibits a type V isotherm with a sudden increase in uptake at ∼50% relative humidity. For humidity levels below this threshold only minor degradation is observed for exposure times up to several hours, suggesting that MOF-5 is more stable than generally assumed under moderately humid conditions. In contrast, irreversible degradation occurs in a matter of minutes for exposures above the 50% threshold. Fourier transform infrared spectroscopy indicates that molecular and/or dissociated water is inserted into the skeletal framework after long exposure times. Densification into pellets can slow the degradation of MOF-5 significantly, and may present a pathway to enhance the stability of some MOFs.

As part of a case-control mortality study of trucking industry workers, exposures to diesel aerosol were measured among the four major presumably exposed job groups (road drivers, local drivers, dock workers, and mechanics) in the industry. Eight industrial hygiene surveys were conducted during both warm and cold weather at eight U.S. terminals and truck repair shops. A single-stage personal impactor was used to sample submicrometer-sized diesel particles on quartz fiber filters. Laboratory and field studies demonstrated that the elemental carbon content of the particles is a useful and practical marker of exposure to vehicular diesel exhaust. A thermal-optical analysis technique was used to determine the concentration of elemental carbon in the filter samples. Overall geometric mean exposures to submicrometer-sized elemental carbon ranged from 3.8 micrograms/m3 in road (long distance) drivers (N = 72) to 13.8 micrograms/m3 in dock workers (N = 75). Geometric mean background area concentrations, measured in the same cities where workers were sampled, were 2.5 micrograms/m3 on major highways (N = 21) and 1.1 micrograms/m3 in residential areas (N = 23). A factorial analysis of variance indicated that exposures in two job groups, dock workers (particularly those exposed primarily via diesel forklift trucks, introduced relatively recently) and mechanics (working in poorly ventilated shops during cold weather), were significantly higher than background concentrations and were significantly higher than the exposures in the local and road drivers. The exposures of the truck drivers could not be distinguished from background highway concentrations but were significantly higher than background concentrations in residential areas.

Autonomous driving (AD) has developed tremendously in parallel with the ongoing development and improvement of deep learning (DL) technology. However, the uptake of artificial intelligence (AI) in AD as the core enabling technology raises serious cybersecurity issues. An enhanced attack surface has been spurred on by the rising digitization of vehicles and the integration of AI features. The performance of the autonomous vehicle (AV)-based applications is constrained by the DL models' susceptibility to adversarial attacks despite their great potential. Hence, AI-enabled AVs face numerous security threats, which prevent the large-scale adoption of AVs. Therefore, it becomes crucial to evolve existing cybersecurity practices to deal with risks associated with the increased uptake of AI. Furthermore, putting defense models into practice against adversarial attacks has grown in importance as a field of study amongst researchers. Therefore, this study seeks to provide an overview of the most recent adversarial defensive and attack models developed in the domain of AD.

Energy management strategies in hybrid electric vehicles determine how much energy is produced/stored/used in each powertrain component. We propose an approach for energy management applied to a series hybrid electric vehicle that aims at improving the powertrain efficiency rather than the total fuel consumption. Since in the series configuration the engine is mechanically decoupled from the traction wheels, for a given power request the steady-state engine operating point is chosen to maximize the efficiency. A control algorithm regulates the transitions between different operating points by using the battery to smoothen the engine transients, thereby improving efficiency. Because of the constrained nature of the transient-smoothing problem, we implement the control algorithm by model predictive control. The control strategy feedback law is synthesized and integrated with the powertrain control software in the engine control unit. Simulations of the urban dynamometer driving schedule (UDDS) and US06 cycles using a complete vehicle system model and experimental tests of the UDDS cycle show improved fuel economy with respect to baseline strategies.

This Special Issue presents papers that cover key features of Cyber - Physical Systems (CPS), including new research and technology advances, open problems, and technical challenges with the papers organized into three categories: theoretical foundations, small-scale applications, and large-scale applications.

Practical use of Bayesian estimation procedures is often associated with difficulties related to elicitation of prior information, and its formalization into the respective prior distribution. The two-parameter Weibull distribution is a particularly difficult case, because it requires a two-dimensional joint prior distribution of the Weibull parameters. The novelty of the procedure suggested here is that the prior information can be presented in the form of the interval assessment of the reliability function (as opposed to that on the Weibull parameters), which is generally easier to obtain. Based on this prior information, the procedure allows constructing the continuous joint prior distribution of Weibull parameters as well as the posterior estimates of the mean and standard deviation of the estimated reliability function (or the CDF) at any given value of the exposure variable. A numeric example is discussed as an illustration. We additionally elaborate on a new parametric form of the prior distribution for the scale parameter of the exponential distribution. This distribution is not a Gamma (as might intuitively be expected); its mode is available in a closed form, and the mean is obtainable through a series approximation.