Mixed‐Norm Spaces and Prediction of SαS Moving Averages

Suppose that is an i.i.d. symmetric α‐stable noise, 1 < α < 2, and consider the moving average process given by . Conditions are obtained for the convergence rate of the moving average series, as well as that of the inverted (autoregressive) representation . These conditions are expressed in terms of the associated function and its reciprocal belonging to certain mixed‐norm spaces of functions on the open unit disc. Properties of these spaces are explored. Criteria are also derived for the rate of mixing in a certain sense.     

A New Covariance Function and Spatio‐Temporal Prediction (Kriging) for A Stationary Spatio‐Temporal Random Process

Consider a stationary spatio‐temporal random process and let be a sample from the process. Our object here is to predict, given the sample, for all t at the location s _o. To obtain the predictors, we define a sequence of discrete Fourier transforms using the observed time series. We consider these discrete Fourier transforms as a sample from the complex valued random variable . Assuming that the discrete Fourier transforms satisfy a complex stochastic partial differential equation of the Laplacian type with a scaling function that is a polynomial in the temporal spectral frequency ω, we obtain, in a closed form, expressions for the second‐order spatio‐temporal spectrum and the covariance function. The spectral density function obtained corresponds to a non‐separable random process. The optimal predictor of the discrete Fourier transform is in terms of the covariance functions. The estimation of the parameters of the spatio‐temporal covariance function is considered and is based on the recently introduced frequency variogram method. The methods given here can be extended to situations where the observations are corrupted by independent white noise. The methods are illustrated with a real data set.     

Counterion-Induced Cationic Flexible Nanoparticle Catalytic of Piperidinolysis of Phenyl Salicylate

The removal of PSa^? from bulk aqueous phase to the pseudo‐micellar phase by halobenzoate counterion X is responsible for the monotonic increase in k_obs (pseudo first‐order rate constants) with the increase in the values of [MX] where MX = sodium salts of 2‐, and 4‐halobenzoic acids. The values of ion exchange constants, or for X = 2‐ and 4‐halobenzoate ions in the presence of tetradecyltrimethylammonium bromide (TTABr) were calculated from the apparent catalytic rate constants, ^Xk_cat which represent the catalytic effect of CFN. Larger values of or were observed for X = 4‐halobenzoate ions than that for X = 2‐halobenzoate ions due to isomeric factors. The values of or determined in the presence of TTABr were compared with previously determined or values in the presence of cetyltrimethylammonium bromide (CTABr). The values of or are nearly 8 ~ 9‐fold larger for 4‐IBz^?, 4‐BrBz^? and 4‐ClBz^? compared to the respective values of X = 2‐IBz^?, 2‐BrBz^? and 2‐ClBz^?. The values of or for X = 4‐FBz^? is nearly 3‐fold larger than that for X = 2‐FBz^?. The values of or for X = 2‐ and 4‐halobenzoates are significantly smaller in the presence of TTABr than these in the presence of CTABr nanoparticles.     

Cointegrated Linear Processes in Hilbert Space

We extend the notion of cointegration for multivariate time series to a potentially infinite‐dimensional setting in which our time series takes values in a complex separable Hilbert space. In this setting, standard linear processes with nonzero long‐run covariance operator play the role of processes. We show that the cointegrating space for an process may be sensibly defined as the kernel of the long‐run covariance operator of its difference. The inner product of an process with an element of its cointegrating space is a stationary complex‐valued process. Our main result is a version of the Granger–Johansen representation theorem: we obtain a geometric reformulation of the Johansen I(1) condition that extends naturally to a Hilbert space setting, and show that an autoregressive Hilbertian process satisfying this condition, and possibly also a compactness condition, admits an representation.     

The role of wettability of nonideal nozzle plate: From drop‐on‐demand droplet jetting to impact on solid substrate

The dynamics of drop‐on‐demand (DoD) droplet formation and subsequently impact on the solid substrate are investigated using a three‐dimensional (3‐D) multirelaxation‐time (MRT) pseudopotential lattice Boltzmann (LB) model. The wettability of nonideal nozzle plate and solid substrate is modeled by a geometric scheme within the LB framework. The dynamics of droplet formation are explored in a range of the inverse of Ohnesorge number , , and , and the Reynolds number , , and . For , no satellite droplet is observed and the wettability of nozzle plate greatly influences the velocity and length of jetting fluids. For , the filament breakup and recombination are observed. The moment of filament breakup is delayed with advancing contact angle increasing. For with , the primary and satellite droplets could not be recombined with and which agree with the literature. Whereas with , the recombination occurs. The dynamics of subsequent oscillating droplet impact on the substrate are similar to that of equilibrium droplet which could obtain high‐resolution printed features. Consequently, considering with large and numbers, the printable range could be extended which could help increase the printing frequency and boost the production outputs of inkjet printing. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2837–2850, 2018     

Mass transfer coefficient of tubular ultrafiltration membranes under high‐flux conditions

The effect of suction flow on the mass transfer coefficient of tubular ultrafiltration membranes, in particular that under a high‐flux condition, was studied. We pointed out that is proportional to under turbulent conditions, and that the proportional constant, b, exceeds 0.023 when the effect of suction flow is not negligible. We conducted the velocity variation method using ultrafiltration membranes with MWCOs of 20k and 100k and dextrans having molecular weights of 40,000 and 70,000 at the conditions, where exceeded . We demonstrated that the effect of suction flow includes not only flux but also the diffusion coefficient of solute, and that the ratio of the flux to the diffusion coefficient, expressed as , is an important index. Finally, we concluded that , when is smaller than , giving the Deissler equation itself, and that , when exceeds . © 2017 American Institute of Chemical Engineers AIChE J, 64: 1778–1782, 2018     

NMR spectroscopic study of chemical equilibria in solutions of formaldehyde,water, and butynediol

Liquid mixtures of formaldehyde, water, and butynediol are complex reacting multicomponent systems in which formaldehyde forms oligomers both with water and butynediol. ‐ and ‐NMR spectra of these mixtures are elucidated. The species distribution of the oligomers is quantitatively determined by ‐NMR spectroscopy. The measurements cover temperatures from 293 to 366 K, overall formaldehyde mass fractions from to , and overall butynediol mass fractions from to . A mole fraction‐based and an activity‐based model of the chemical equilibrium in the studied system are developed and chemical equilibrium constants are reported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4442–4450, 2017     

Defect engineering on phase structure and temperature stability of KNN‐based ceramics sintered in different atmospheres

Lead‐free MnO‐doped 0.955K_0.5Na_0.5NbO₃‐0.045Bi_0.5Na_0.5ZrO₃ (Abbreviated as KNN‐0.045BNZ) ceramics have been prepared by the conventional solid‐state sintering method in reducing atmosphere ( = 1 × 10^?10 atm) and air. For ceramics sintered in reducing atmosphere, only Mn²⁺ ions exist in ceramics who preferentially occupy the cation vacancies in A‐site at x = 0.2‐0.4, whereas Mn²⁺ ions substitute for Zr⁴⁺ ions in B‐site to form defects () at x > 0.4. For ceramics sintered in air, mixed Mn²⁺, Mn³⁺, and Mn⁴⁺ ions coexist here. The Mn²⁺ ions preferentially occupy the cation vacancies in A‐site at x = 0.2‐0.4 and then Mn²⁺ ions substitute for Zr⁴⁺ ions in B‐site at x > 0.4. Meanwhile, the Mn³⁺ ions and Mn⁴⁺ ions substitute for Nb⁵⁺ ions in B‐site to form defects () at x = 0.2‐0.8. The (, , and ) dipolar defects show a positive dipolar defect contribution (DDC) to the , whereas the dipolar defects () show a negative DDC to the . The dipolar defects ( ‐ and ) can help improve the temperature stability of . The 0.4% MnO‐doped KNN‐0.045BNZ ceramics sintered in reducing atmosphere show excellent piezoelectric constant d₃₃ = 300 pC/N and 0.2% MnO‐doped KNN‐0.045BNZ ceramics sintered in air possess optimal piezoelectric constant d₃₃ = 290 pC/N.     

Cationic effect of charge compensation on the sulfide capacity of aluminosilicate slags

The effect of CaO on the sulfide capacity of CaO‐Al₂O₃‐SiO₂ slags was studied from the viewpoint of the ionic structure of alumina in slag. The aluminum coordination number was analyzed using ²⁷Al 500‐MHz solid nuclear magnetic resonance spectroscopy and the results were compared with those of the sulfide capacity analysis. The sulfide capacity of slag, in the peralkaline region (), exhibited a linear relationship with respect to basicity () as excess free Ca²⁺ formed a 4‐coordinated aluminum unit structure (^[IV]Al; ) and stabilized the sulfide ions (). However, sulfide capacity in the peraluminous region () exhibited a nonlinear relationship with respect to basicity () owing to the structure of higher‐coordinated aluminum units (^[V]Al, ^[VI]Al; Al³⁺) and the relative lack of Ca²⁺. Therefore, the sulfide capacity of high Al₂O₃‐bearing slags strongly depended on the basicity () and stability of sulfide ions (), which depended on the competitive behavior of Ca²⁺ owing to the structural changes in Al₂O₃. The effect of the aluminum coordination number on the sulfide capacity was discussed in detail using an analysis of the slag structure and thermodynamics model.     

Domain engineering enhanced microwave tunability in nonstoichiometric Ba0.8Sr0.2TiO3

Domain engineering via oxygen vacancy, , loading achieved by A/B modification as well as quenching treatment, was utilized for Ba_0.8Sr_0.2TiO₃ (0.8 BSTs) in an attempt to enhance the microwave tunable characteristics. For similar grain sizes, the domain sizes were notably reduced for all nonstoichiometric BSTs, indicating that the loaded (as a consequence of Ti defects, ) played a role in the nuclei for new domain walls. The tunability T at 100 MHz under a direct current field of 30 V/20 μm increased steadily as the domain size (d.s.) declined for all BSTs, regardless of the A/B ratio, due to the d.s. effect. The tunable characteristics in nonstoichiometric BSTs having a similar d.s. of ?190 nm were then compared. The tunability and tan δ decreased for A/B = 1.002 (0.2 mol% Ti defects). The introduced formed pinning centers that restricted domain wall motion, leading directly to lower tunability and smaller dielectric loss. However, ‐overloaded samples (i.e., A/B ≥ 1.005) exhibited increased values for tan δ due to conduction in the domains. The quench treatment of 0.8 BST (with A/B = 1.002) samples resulted in a d.s. reduction from 191 to 170 nm. These quenched specimens showed greater tunability, T_total, originating from the strengthened dipole contribution, T_dipole, as a consequence of the d.s. effect. The tan δ of the quenched specimens was essentially unchanged, indicating a homogenous distribution via the quench, effectively reducing the mobile (which contributes to electrical conduction) in the domains. Consequently, the achieved figure of merit via domain engineering was 2.25 at 100 MHz for the quenched BST with A/B = 1.002, which was 1.54 times larger than that of unmodified BST.     

Removal of NO from flue gas using UV/S2 process in a novel photochemical impinging stream reactor

A novel photochemical impinging stream reactor was developed for the first time. Removal process of NO from flue gas using sulfate radical ( ·) and hydroxyl radical (·OH) from UV‐light activation of persulfate (UV/S₂ advanced oxidation process) was investigated in the novel reactor. Experiments were conducted to evaluate the effects of S₂ concentration, solution pH, UV power, solution temperature, liquid‐gas ratio, flue gas flow, NO, SO₂,and O₂ concentrations on removal of NO. Mechanism and kinetics of NO removal were also studied. The results show that increasing UV power, solution temperature, S₂ concentration, or solution circulation rate promotes NO removal. Increasing solution pH (1.2–11.9), NO concentration or flue gas flow weakens NO removal. O₂ concentration has no significant effect on NO removal. · and ·OH were the major active species for NO removal. Absorption rate equation and kinetic parameters of NO removal were obtained. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2968–2980, 2017     

First‐principles investigation of the thermodynamic stability of MB2 materials surfaces (M = Ti/Zr/Hf)

Some of the renewed interest in transition metal diborides (MB₂, M = Ti/Zr/Hf) arises from their potential use as matrices in ultrahigh‐temperature ceramic matrix composites (UHTCMCs). Crucial to the understanding of such composites is the study of the fiber/matrix interfaces, which in turn requires a deep knowledge of the surface structures and the thermodynamics of the matrix material. Here we investigate the surface stability of MB₂ compounds by first‐principles calculations. Five surfaces are stabilized when going from a M‐rich to a B‐rich environment, respectively (0001)_M, (100)_M, (101)_B(M), (113)_M and (0001)_B, with the highly stable (100)_M, (101)_B(M) and (113)_M surfaces being discussed here for the first time. The mechanism behind the surface stability is analyzed in terms of cleavage energy, surface strain and surface bonding states. Our results provide important information for a better understanding of the most likely surfaces exposed to the fibers in UHTCMCs, thereby for the construction of reliable interfaces and ultimately UHTCMCs models.     

Pressure drop through platinized titanium porous electrodes for cerium‐based redox flow batteries

The pressure drop, , across a redox flow battery is linked to pumping costs and energy efficiency, making fluid properties of the electrolyte important in scale‐up operations. The at diverse platinized titanium electrodes in Ce‐based redox flow batteries is reported as a function of mean linear electrolyte velocity measured in a rectangular channel flow cell. Darcy's friction factor and permeability vs. Reynolds number are calculated. Average permeability values are: 7.10 × 10^?4 cm² for Pt/Ti mesh, 4.45 × 10^?4 cm² for Pt/Ti plate + turbulence promoters, 1.67 × 10^?5 cm² for Pt/Ti micromesh, and 1.31 × 10^?6 cm² for Pt/Ti felt. The electrochemical volumetric mass transport coefficient, , is provided as a function of . In the flow‐by configuration, Pt/Ti felt combines high values with a relatively high , followed by Pt/Ti micromesh. Pt/Ti mesh and Pt/Ti plate gave a lower but poorer electrochemical performance. Implications for cell design are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1135–1146, 2018     

Self‐synthesized epoxy terminated polydimethylsiloxane with various molecular weights toughening epoxy resin

Polydimethylsiloxane terminated by epoxy group (EP‐PDMS) with various molecular weight ( ) were synthesized by 1,3‐bis[3‐(2,3‐epoxypropoxy)‐propyl]‐1,1,3,3‐tetramethyldisiloxane (DOTMDS) and dimethylcyclosiloxane (D_n). The epoxy value measured by potentiometric titration, were 0.161, 0.092, 0.065, 0.044 mol/100 g, and the (calculated from epoxy value) 1,242, 2,174, 3,077, 4,545 g/mol, respectively (corresponding to EP‐PDMS1, 2, 3, 4). With the increasing ratio of D_n/DOTMDS, we can see the increase of and the decrease of epoxy group content according to FTIR result. Then these EP‐PDMS were used to improve the toughness of the epoxy resin (diglycidyl ether of bisphenol A, DGEBA). Mechanical tests showed that, the impact strength of the epoxy resin was improved by EP‐PDMS. The toughening effect was decreased when EP‐PDMS with relative higher was used. This was ascribed to that the EP‐PDMS with high was easier to agglomerate, and the active group was easier to be embedded which in turn resulted in lower toughening efficiency. This was also confirmed by scanning electron microscopy results. J. VINYL ADDIT. TECHNOL., 24:268–274, 2018. © 2016 Society of Plastics Engineers     

Compressive shape memory behavior of spring‐shaped polylactic acid alloy type

This article presents an experimental study on the shape memory behavior of blends of thermoplastic polyurethane (TPU) and biodegradable polylactic acid (PLA) at the PLA/TPU weight ratios of 70/30 (PT7030) and 50/50 (PT5050). The manufactured springs were studied comprehensively based on their morphological and thermal properties. Scanning electron microscopy micrographs were captured, which verified that TPU was compatible with PLA. The wide‐angle X‐ray diffraction suggested that the crystallinity of PLA was enhanced in the presence of TPU. In order to determine the shape recovery properties [shape recovery ratio (R_r), shape fixing ratio (R_f), and shape recovery force (F_r)], the samples programmed at three different temperatures (T_p) of 70, 80, and 90 ° and at various recovery temperatures (T_r) over 40 to 90 ° , were studied. In general, the spring made with PT7030 showed higher R_r, R_f, and F_r values. The highest R_r (99%) was obtained at programmed temperature (T_p) of 70 ° and recovery temperature (T_r) of 90 ° . However, the R_r value for this spring programmed at 70 ° and recovered near body temperature was 50% with F_r of 1.4 N. Furthermore, the highest F_r (15.6 N) was observed in the spring made of PT7030 programmed at 80 ° and recovered at T_r of 78 ° . © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45115.     

A positron emission particle tracking investigation of the scaling law governing free surface flows in tumbling mills

Positron Emission Particle Tracking (PEPT) measurements are used to track the flow of glass beads within a rotating drum fitted with (and without) lifter bars and operated in the cascading and cataracting Froude regimes. After converting the Lagrangian trajectories of a representative radio‐labeled glass bead (the tracer) into Eulerian fields under the ergodic assumption, the bed shape and kinematics are extracted for steady, fully developed flow conditions. Notwithstanding the azimuthal wall effects introduced by the lifter bars, we show a linear scaling of the local flowing layer thickness (h) with local depth‐averaged velocity and a constant average shear for direct measurements spanning the entire flowing layer (not just the central region), and high Froude regimes (cascading and cataracting) not previously investigated by scaling analysis in the literature. © 2016 American Institute of Chemical Engineers AIChE J, 63: 903–913, 2017     

A rigorous method to evaluate the consistency of experimental data in phase equilibria. Application to VLE and VLLE

This work forms part of a broader study that describes a methodology to validate experimental data of phase equilibria for multicomponent systems from a thermodynamic‐mathematical perspective. The goal of this article is to present and justify this method and to study its application to vapor–liquid equilibria (VLE) and vapor–liquid–liquid equilibria (VLLE), obtained under isobaric/isothermal conditions. A procedure based on the Gibbs‐Duhem equation is established which presents two independent calculation paths for its resolution: (a) an integral method and (b) a differential method. Functions are generated for both cases that establish the verification or consistency of data, δψ for the integral test and δζ for the differential approach, which are statistically evaluated by their corresponding average values [ , ], and the standard deviations [ , ]. The evaluation of these parameters for application to real cases is carried out using a set of hypothetical systems (with data generated artificially), for which the values are adequately changed to determine their influence on the method. In this way, the requirements of the proposed method for the data are evaluated and their behavior in response to any disruption in the canonical variables (p,T, phase compositions). The conditions for thermodynamic consistency of data are: , , , and . In systems with VLLE, in addition to the previous criteria, must occur that: and . The new proposed method has been tested with a set of 300 experimental binary systems, biphasic and triphasic, obtained from published bibliography, and the results are compared with those of other tests commonly used for testing thermodynamic consistency. The results show that the greater rigor of the proposed method is mainly due to the simultaneous verification of various independent variables. As a result, the conditions for the new test are verified for fewer systems than using other tests mentioned in the literature (i.e., Fredenslund‐test and direct of Van Ness). Its unique application is sufficient to ensure the consistency of experimental data, without using other tests. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

On Asymptotic Theory for ARCH (∞) Models

Autoregressive conditional heteroskedasticity (ARCH)() models nest a wide range of ARCH and generalized ARCH models including models with long memory in volatility. Existing work assumes the existence of second moments. However, the fractionally integrated generalized ARCH model, one version of a long memory in volatility model, does not have finite second moments and rarely satisfies the moment conditions of the existing literature. This article weakens the moment assumptions of a general ARCH( ) class of models and develops the theory for consistency and asymptotic normality of the quasi‐maximum likelihood estimator.     

A piezomicrobalance system for high‐temperature mass relaxation characterization of metal oxides: A case study of Pr‐doped ceria

A system for mass relaxation studies based on a gallium phosphate piezocrystal microbalance has been developed, built, and successfully used to characterize a representative mixed ionic and electronic conducting material. The apparatus is constructed to achieve reactor gas exchange times as short as 2 seconds and temporal resolution in mass measurement of 0.1 seconds. These characteristics enabled evaluation of mass relaxations that occurred on the 6 seconds time scale. Proof of concept for materials characterization capabilities of the system was carried out using 10% praseodymium‐doped cerium oxide (PCO), a material that undergoes, at selected temperatures and oxygen partial pressures, changes in mass but not in conductivity. Thin films were deposited on the piezocrystals via pulsed laser deposition (PLD). Mass relaxation curves were collected at 700°C upon application of a small step change in oxygen partial pressure, . Using two different films, the surface reaction constant, k_S, was obtained over the range from 10^?4 to 0.1 atm. Its value is found to vary between 9.7 × 10^?6 and 1.7 × 10^?4 cm/s, displaying a power law dependence on , with a law exponent of 0.67 ± 0.02, as averaged over the two sets of results. This steep dependence of k_S on is surprisingly independent of a change in dominant defect type within the range of measurement.     

Imidazolium‐Based Ionic Liquid as Modulator of Physicochemical Properties of Cationic,Anionic, Nonionic,and Gemini Surfactants

The aggregation morphology of 2 cationic surfactants (cetyldimethylethanolammonium bromide and cetyldiethylethanolammonium bromide), an anionic surfactant (sodium dodecylbenzenesulfonate), a nonionic surfactant (Triton X‐100), and 2 gemini surfactants (16‐4‐16,2Br^?[butanediyi‐1,4‐bis(dimethyldohexylammonium bromide)] and 16‐6‐16,2Br^?[hexanediyi‐1,6‐bis(dimethyldohexylammonium bromide)]) in the presence of the ionic liquid (IL) 1‐ethyl‐3‐methylimidazoliumbromide [Emim][Br] is studied using various techniques such as surface tension, conductivity, and UV–visible and fluorescence spectroscopy. Increasing the concentration of [Emim][Br] results in a decrease in the critical micelle concentration (CMC) value of the surfactants. Various interfacial properties, namely the surface excess concentration (Г_max), minimum area per molecule at the air–water interface (A_min)_, and surface pressure at the CMC (π_cmc), as well as the thermodynamic parameters such as free energy of the given air/water interface (), Gibbs free energy of micelle formation (), Gibbs free energy of micellization per alkyl tail (), Gibbs energy of transfer (), and standard free energy of adsorption () were also investigated. The aggregation number (N_agg) was determined by the fluorescence method. It was observed that N_agg decreased with increasing weight‐percent of the IL.