Interest For Many Applications Research Articles

Synthesis of transparent oil dispersion of monodispersed calcium carbonate nanoparticles with high concentration

The preparation of monodispersed inorganic nanoparticles is of great interest for many applications. In this article, transparent oil dispersion of monodispersed amorphous CaCO3 nanoparticles with high concentration and long‐term stability were controllably prepared by a reverse microemulsion method. The effects of the addition amount of extra minute water and (NH4)2CO3 as novel assistant promoter, reaction temperature, Ca(OH)2/CaO mole ratio were explored. The optimum synthesis conditions were achieved. The as‐prepared transparent oil nanodispersion had a good monodispersity, a uniform particle size of 8–10 nm, a high stability of over 12 months, a high solid content of 38 wt% (Ca content of about 15.5 wt%) and a high total base number of 416 mgKOH/g. The preparation process was further investigated by polarized optical microscope and Fourier transform infrared. This nanodispersion will find a promising applicability as an excellent nanodetergent in the fields of automobile and marine lubricants. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3663–3669, 2017

Temperature-dependent self-assembly and rheological behavior of a thermoreversible pmma-PnBA-PMMA triblock copolymer gel

Self-assembly and mechanical properties of triblock copolymers in a mid-block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–PnBA–PMMA] in two different mid-block selective solvents, n-butanol and 2-ethyl-1-hexanol. Gel formation resulting from end-block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of −80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear-rheometry, thermal analysis, and small-angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state to a gel state to a percolated cluster network with decrease in temperature. The aggregated PMMA end-blocks display a glass transition temperature. Our results provide new understanding into the structural changes of a self-assembled triblock copolymer gel over a large length scale and wide temperature range. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 877–887

Synthesis and spectral evaluation of 5,10,15,20-tetrakis(3,4-dibenzyloxyphenyl)porphyrin

Abstract Porphyrins are of interest in many applications that involve electron transfer and absorption of light, such as solar energy and photodynamic cancer therapy. The newly synthesized 5,10,15,20-tetrakis(3,4-dibenzyloxyphenyl)porphyrin, TDBOPP, was characterized using 1H NMR, 13C NMR, UV-vis and fluorescence spectroscopy and MALDI-TOF/TOF high resolution mass spectrometry. Standard 1H NMR and 13C NMR experiments coupled with nuclear Overhauser effect (NOE) experiments confirmed the structure of the compound. The expected M+ and [M+H]+ ions are observed in the MALDI-TOF/TOF mass spectrum. The UV-vis absorption spectrum of TDBOPP shows a Soret band at 424 nm and three Q bands at 519 nm, 556 nm, and 650 nm with molar absorptivity 3.6×105 cm−1 m −1, 1.6×104 cm−1 m −1, 1.0×104 cm−1 m −1 and 5.3×103 cm−1 m −1, respectively. Excitation at 424 nm gives emission at 650 nm. The quantum yield of the porphyrin is 0.11.

Method for the Thermal Characterization of PCM Systems in the Volume Range from 100 ml to 1000 ml

The storage of latent heat in phase change materials (PCM) is of great interest in many applications, for example in building applications. However, there is no standard method for the determination of the thermophysical properties of application-sized PCM specimens, i.e., specimens with sizes around 100 ml to 1000 ml. In order to close this metrological gap, a commercially available heat flow meter was modified to perform enthalpy measurements. The feasibility of this method was proven by performing comparative measurements on a stainless steel specimen using both the standard method DSC and the modified heat flow meter. Furthermore, measurements on a gypsum board with microencapsulated PCM were performed with the heat flow meter in order to determine the enthalpy. The coincidence with literature values is within ±4% which demonstrates that this method is a good choice for performing measurements on application-sized PCM specimens.

Tailoring the nonlinear response of MEMS resonators using shape optimization

We demonstrate systematic control of mechanical nonlinearities in micro-electromechanical (MEMS) resonators using shape optimization methods. This approach generates beams with non-uniform profiles, which have nonlinearities and frequencies that differ from uniform beams. A set of bridge-type microbeams with selected variable profiles that directly affect the nonlinear characteristics of in-plane vibrations was designed and characterized. Experimental results have demonstrated that these shape changes result in more than a three-fold increase and a two-fold reduction in the Duffing nonlinearity due to resonator mid-line stretching. The manipulation of this nonlinearity has significant interest in many applications, including precise mass sensing, accurate measurement of angular rates, and timekeeping.

The weight hierarchy of a family of cyclic codes with arbitrary number of nonzeroes

The generalized Hamming weights (GHWs) are fundamental parameters of linear codes. GHWs are of great interest in many applications since they convey detailed information of linear codes. In this paper, we continue the work of [10] to study the GHWs of a family of cyclic codes with arbitrary number of nonzeroes. The weight hierarchy is determined by employing a number-theoretic approach.

Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

The production of singlet delta oxygen (O2(a1Δg)) is of growing interest for many applications. We report on the measurement of O2(a1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a1Δg) production. Different O2(a1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a1Δg) densities are discussed. The flow rate also allows for control of the O2(a1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

On a generalization of the maximum entropy Theorem of Burg

In this article we introduce some matrix manipulations that allow us to obtain a version of the original Christoffel-Darboux formula, which is of interest in many applications of linear algebra. Using these developments matrix and Jensen’s inequality, we obtain the main result of this proposal, which is the generalization of the maximum entropy theorem of Burg for multivariate processes.

Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control.

Mussel adhesive proteins are of great interest in many applications because of their outstanding adhesive property and film-forming ability. Understanding and controlling the film formation and its performance is crucial for the effective use of such proteins. In this study, we focus on the potential controlled film formation and compaction of one mussel adhesive protein, Mefp-1. The adsorption and film-forming behavior of Mefp-1 on a platinum (Pt) substrate under applied potentials were investigated by cyclic voltammetry, potential-controlled electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Moreover, microfriction measurements were performed to evaluate the mechanical properties of the Mefp-1 films formed at selected potentials. The results led to the conclusion that Mefp-1 adsorbs on the Pt substrate through both electrostatic and nonelectrostatic interactions and shows an effective blocking effect for the electroactive sites on the substrate. The properties of the adsorbed Mefp-1 film vary with the applied potential, and the compactness of the adsorbed Mefp-1 film can be reversibly tuned by the applied potential.

Carrier statistics in graphene at high electric field

The saturated velocity of a semiconductor is an important measure of performance. Graphene has been of interest for many applications due to its apparently high value of the saturated velocity. Recent experiments have suggested that this value is very density dependent and can even exceed the band limiting Fermi velocity. On the other hand, recent calculations have shown that the saturated velocity is largely independent of the carrier density. Here, we show that the carrier heating, due to high electric fields, can change the carrier statistics. This, and the fact that minority carriers can significantly impact the conductance may lead to erroneous conclusions about the actual total carrier density in the experimental situation.

Over 19 W Single-Mode 1545 nm Er,Yb Codoped All-Fiber Laser

We report a high-power cladding-pumped Er,Yb codoped all-fiber laser with truly single transverse mode output. The fiber laser is designed to operate at 1545 nm by the use of a pair of fiber Bragg gratings (FBGs) to lock and narrow the output spectrum, which can be very useful in generating the eye-safe ~1650 nm laser emission through the Stimulated Raman Scattering (SRS) in silica fibers that is of interest in many applications. Two pieces of standard single-mode fibers are inserted into the laser cavity and output port to guarantee the truly single-mode output as well as good compatibility with other standard fiber components. We have obtained a maximum output power of 19.2 W at 1544.68 nm with a FWHM spectral width of 0.08 nm, corresponding to an average overall slope efficiency of 31.9% with respect to the launched pump power. This is, to the best of our knowledge, the highest output power reported from simple all-fiber single-mode Er,Yb codoped laser oscillator architecture.

A novel adenine-based zinc(II) metal-organic framework featuring the Lewis basic sites for heterogeneous catalysis

Metal-organic frameworks (MOFs), as a new sort of crystalline materials, have attracted lots of interest in many applications during the past decades. Recently, many efforts have been focused on the development of MOFs as heterogeneous catalysis. In this communication, we selected adenine (ad) and tetracarboxylic acid, namely 5,5′-(1,3,6,8-tetraoxobenzo[Imn] Li et al. (1999), He et al. (2016) phenanthroline-2,7-diyl)bis-1,3-benzenedicarboxylic acid (H4L), as organic linkers to assemble with Zn(II) ions to construct a novel adenine-based porous MOF. There are three different inorganic clusters in the framework, including ZnO2N2, Zn2O2N6, and ZnO5N clusters. Interesting, the resultant porous MOF, namely [H2N(CH3)2]⋅[Zn4(L)1.5(ad)3(H2O)2]⋅4DMF, retains free amino groups in the framework, which can be served as Lewis basic sites to catalyse Knoevenagel condensation reaction. The catalytic study exhibits that the as-synthesized MOF with free amino groups can be used as heterogeneous catalysis with remarkable catalytic efforts and good recycle.

The cylindrical $K$-function and Poisson line cluster point processes

The analysis of point patterns with linear structures is of interest in many applications. To detect anisotropy in such patterns, in particular in the case of a columnar structure, we introduce a functional summary statistic, the cylindrical $K$-function, which is a directional $K$-function whose structuring element is a cylinder. We further introduce a class of anisotropic Cox point processes, called Poisson line cluster point processes. The points of such a process are random displacements of Poisson point processes defined on the lines of a Poisson line process. Parameter estimation for this model based on moment methods or Bayesian inference is discussed in the case where the underlying Poisson line process is latent. To illustrate the proposed methods, we analyse two- and three-dimensional point pattern datasets. The three-dimensional dataset is of particular interest as it relates to the minicolumn hypothesis in neuroscience, which claims that pyramidal and other brain cells have a columnar arrangement perpendicular to the surface of the brain.

Reinforcement and shape stabilization of phase-change material via graphene oxide aerogel

Phase change materials (PCMs) are of interest in many applications which may require shape-stabilization. In this study, a graphene oxide aerogel (GOxA) reinforced paraffin PCM composite is developed, effectively reinforcing and shape-stabilizing the paraffin.The molecular and diffraction characterizations suggest that the GOxA network potentially affects paraffin's crystallization. The mechanical characterizations using durometer and nanoindentation show that the composite is 3∼7× harder than pure paraffin and maintains significant strength even above paraffin's melting temperature. Moreover, the composite is much less strain-rate sensitive than paraffin. The reinforcement via GOxA is much beyond the prediction by the rule-of-mixture, implying a strong GOxA-paraffin interfacial bonding.To our best knowledge, this is the first study on the mechanical behavior of paraffin and GOxA-PCM composite, providing critical insights into their behavior. Additionally, the relationship between the hardness and durometer index first-ever developed here will enable the quantitative durometer testing on materials for many other applications at different ambient conditions due to its versatility and simplicity.

Organocatalytic Coupling of CO2 with Oxetane.

The organocatalytic coupling of CO2 with oxetanes is investigated under solvent-free conditions. The influence of the main reaction parameters (type of organocatalytic system, pressure, and temperature) on the yield, the product formed, and the selectivity of the reaction are discussed. An onium salt combined with a fluorinated alcohol promotes the efficient and selective organocatalytic synthesis of α,ω-hydroxyl oligocarbonates by coupling CO2 with oxetanes at 130 °C and at a CO2 pressure as low as 2 MPa. NMR characterizations were correlated with matrix-assisted laser desorption/ionization with time-of-flight mass spectrometer (MALDI-TOF) analyses for elucidating the structure of the oligomers. Online FTIR studies under pressure, NMR titrations, and DFT calculations allowed an in-depth understanding of the reaction mechanism. Finally, CO2 -based poly(carbonate-co-urethane)s were synthesized by step-growth polymerization of hydroxyl telechelic oligocarbonates with 4,4'-methylene diphenyl diisocyanate (MDI). The organocatalytic system described herein constitutes an innovative sustainable route to the selective preparation of hydroxyl telechelic carbonates of high interest for many applications, notably for the polyurethane business (especially for coatings or foams).

Performance characterization of a novel Fe-based sorbent for anaerobic gas desulfurization finalized to high temperature fuel cell applications

A novel sorbent (SCX) composed of mixed iron oxides and hydroxides was studied to assess its suitability for H2S removal from biogas finalized to high temperature fuel cell systems. From an industrial point of view, the potential usage of this product would have a beneficial impact on operational costs, since it is less expensive than activated carbons. Moreover, it is a non-hazardous landfilled product with a reduced environmental impact and it can be easily regenerated.Sorbent SCX was tested in different operative conditions, evaluating the influence on sorption capacity of gas hourly space velocity (GHSV), gas composition (inlet H2S concentration, gas matrix, humidity), reactor temperature and filter geometry. As main outcomes, the experimentation highlighted: i) a hyperbolic increase in adsorption capacity as GHSV decreased, ii) a parabolic performance enhancement with increasing temperature and iii) a negative effect of humidity.Moreover, a comparison with commercial activated carbons typically used for the same purpose (Cu–Cr or KOH–KI treated) was performed, identifying the optimal operative parameters to obtain higher H2S sorption capacity for SCX sorbent. Specifically, SCX showed its potential in terms of H2S removal for GHSV lower than 330 h−1, values of particular interest for many practical applications. In this case, an improved removal capability is obtained with respect to the ones exhibited by the considered carbons. Moreover, quantitative evaluations provided for unitary installed power (1 kWe fuel cell-based systems) highlighted the possibility to have more compact (volume reduction of about 50%) and cheaper (cost reduction up to six times) filters.

Tunable Complete Optical Absorption in Multilayer Structures Including Ge2Sb2Te5 without Lithographic Patterns

Controlling the spectral transmission, reflection, and absorption properties of optical structures is of great interest for many applications in photonics. Particularly, perfect absorbers over a wide frequency (wavelength) range are desirable for thin-film thermal emitters, thermo-solar cells, photodetectors, and smart windows. Up to date, several mechanisms have been proposed to achieve nearly 100% absorption in various frequency ranges of the electromagnetic spectrum; starting from microwaves to near infrared (NIR) and visible. One of the first demonstrations of a structure that was absorbing with nearly 100% efficiency was proposed by Landy et al. in 2008,[1] where metamaterial resonator arrays were used to achieve narrowband and highly resonant absorption of GHz and THz waves. The narrowband character of the resonances can be an advantage when absorbers with high quality factor are required and wavelength selectivity is desirable. However, there are many applications that need broadband absorption. To this end great efforts have been made during the last decade, for instance by mixing multiple resonances in a many-fold resonator, which can lead to, e.g., dual band[2] or multiband[3-9] resonant absorption. Unfortunately fabrication of these structures requires sophisticated techniques such as micro- or nano-lithography, severely limiting their scalability and increasing the cost of the absorber.

Multibody modelling of an internal gyroscopic micro-mechanism for development of lateral deviation of a projectile

The lateral control of a projectile for targeting and impacting a nonstationary target is of interest in many applications. Through the use of internal moving parts, gyroscopic forces can be generated, thus changing the flight trajectory of the projectile. In this study, three small internal swing masses are introduced to the projectile and their motions are controlled. The masses are attached to the end of massless rods that are located on points of an equilateral triangle centered about the major axis of the projectile. A mathematical model for the internal gyroscopic rotating disks of this multibody mechanism and its trajectory path is presented. For this mechanism, the dynamics equations of motion are developed and solved numerically to simulate the trajectory of the projectile. The concept projectile model is shown to move cyclically about the axis of rotation and to deviate from its axis in a relatively even slope. A parametric study is then focused on actuating each mass in sequence or changing the weight of the masses and their initial positions to examine and evaluate the flight trajectory of the projectile. The results from this study show that the lateral deviation of a projectile can be controlled by altering the initial configuration of the rotating mass mechanism. This application may hold merit for controlling the re-entry flight trajectory of air vehicles.

Transparent, superhydrophobic, and wear-resistant surfaces using deep reactive ion etching on PDMS substrates

Surfaces that simultaneously exhibit superhydrophobicity, low contact angle hysteresis, and high transmission of visible light are of interest for many applications, such as optical devices, solar panels, and self-cleaning windows. Superhydrophobicity could also find use in medical devices where antifouling characteristics are desirable. These applications also typically require mechanical wear resistance. The fabrication of such surfaces is challenging due to the competing goals of superhydrophobicity and transmittance in terms of the required degree of surface roughness. In this study, deep reactive ion etching (DRIE) was used to create rough surfaces on PDMS substrates using a O2/CF4 plasma. Surfaces then underwent an additional treatment with either octafluorocyclobutane (C4F8) plasma or vapor deposition of perfluorooctyltrichlorosilane (PFOTCS) following surface activation with O2 plasma. The effects of surface roughness and the additional surface modifications were examined with respect to the contact angle, contact angle hysteresis, and optical transmittance. To examine wear resistance, a sliding wear experiment was performed using an atomic force microscope (AFM).

The Weight Hierarchy of Some Reducible Cyclic Codes

The generalized Hamming weights (GHWs) of linear codes are fundamental parameters, the knowledge of which is of great interest in many applications. However, to determine the GHWs of linear codes is difficult in general. In this paper, we study the GHWs for a family of reducible cyclic codes and obtain the complete weight hierarchy in several cases. This is achieved by extending the idea of Yang et al. into higher dimension and by employing some interesting combinatorial arguments. It shall be noted that these cyclic codes may have arbitrary number of nonzeros.