A soluble and multichromic conducting polythiophene derivative

A new soluble polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1-4-nitrophenyl-2,5-di(2-thienyl)-1H-pyrrole (SNSNO₂). Chemical method produces a polymer which is completely soluble in organic solvents. The structures of both the monomer and the soluble polymer were elucidated by ¹H and ¹³C-NMR and FTIR. The average molecular weight has been determined by GPC to be Mn = 6.3 × 10³ for the chemically synthesized polymer. P(SNSNO₂) was also synthesized via potentiostatic electrochemical polymerization. Characterizations of the resulting polymer were performed by cyclic voltammetry CV, FTIR and UV-Vis spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. In addition, dual type polymer electrochromic devices ECDs based on P(SNSNO₂) with poly3,4-ethylenedioxythiophene (PEDOT) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.     

Nitro Derivatives of Parabanic Acid as Potential Explosives: A Theoretical Study

This work deals with certain parabanic acid (PA) derivatives because they possess great calculated density (>1.8 g · cm^–3) and high content of nitrogen (26 %). Computed ballistic properties of eight different parabanic acid derivatives are presented. The structures were optimized at the B3LYP/6‐31G(d, p) level. The calculated data for PA are found to be compatible with the experimental X‐ray data. The detonation performance analyses were done using empirical Kamlet‐Jacobs equations. Additionally, detonation products were assigned and power index were calculated. All the compounds considered are powerful candidates for high energy materials.     

Performing thermodynamic analysis by simulating the general characteristics of the two-spool turbojet engine suitable for drone and UAV propulsion

Journal of Thermal Analysis and Calorimetry - This study presents determining performance parameters as well as thermodynamic analysis through certain design parameters of a two-spool turbojet...     

Bifunctional polytetrahydrofuran initiator for sequential photochemical and thermal initiation

The polymerization of tetrahydrofuran was initiated with 4,4′-azobis(4-cyanovaleryl chloride) in conjunction with silver hexafluoroantimonate and the living polytetrahydrofuran (PTHF) was terminated with pyridinium N-oxide derivatives. The resulting PTHF-macroinitiator possesses both a thermally and photochemically labile group.     

The Measurement of Ultrashort Light Pulses—Simple Devices,Complex Pulses

We review the state of the art of ultrashort-light-pulse measurement using frequency-resolved-optical-gating (FROG). Recent developments have extended the state of the art considerably. FROG devices for measuring the intensity and phase of ultrashort laser pulses have become so simple that almost no alignment is required. In addition, such devices not only operate single shot, but they also yield the two most important spatio-temporal distortions, spatial chirp and pulse-front tilt. With other FROG variations, it is now possible to measure more general ultrashort light pulses (i.e., pulses much more complex than common laser pulses), with time-bandwidth products as large as several thousand and as weak as a few hundred photons, and despite other difficulties such as random absolute phase and poor spatial coherence.     

Efficient algorithms for robust and stable principal component pursuit problems

The problem of recovering a low-rank matrix from a set of observations corrupted with gross sparse error is known as the robust principal component analysis (RPCA) and has many applications in computer vision, image processing and web data ranking. It has been shown that under certain conditions, the solution to the NP-hard RPCA problem can be obtained by solving a convex optimization problem, namely the robust principal component pursuit (RPCP). Moreover, if the observed data matrix has also been corrupted by a dense noise matrix in addition to gross sparse error, then the stable principal component pursuit (SPCP) problem is solved to recover the low-rank matrix. In this paper, we develop efficient algorithms with provable iteration complexity bounds for solving RPCP and SPCP. Numerical results on problems with millions of variables and constraints such as foreground extraction from surveillance video, shadow and specularity removal from face images and video denoising from heavily corrupted data show that our algorithms are competitive to current state-of-the-art solvers for RPCP and SPCP in terms of accuracy and speed.     

Time-Dependent Shape Factors for Uniform and Non-Uniform Pressure Boundary Conditions

Matrix–fracture transfer functions are the backbone of any dual-porosity or dual-permeability formulation. The chief feature within them is the accurate definition of shape factors. To date, there is no completely accepted formulation of a matrix–fracture transfer function. Many formulations of shape factors for instantly-filled fractures with uniform pressure distribution have been presented and used; however, they differ by up to five times in magnitude. Based on a recently presented transfer function, time-dependent shape factors for water imbibing from fracture to matrix under pressure driven flow are proposed. Also new matrix–fracture transfer pressure-based shape factors for instantly-filled fractures with non-uniform pressure distribution are presented in this article. These are the boundary conditions for a case for porous media with clusters of parallel and disconnected fractures, for instance. These new pressure-based shape factors were obtained by solving the pressure diffusivity equation for a single phase using non-uniform boundary conditions. This leads to time-dependent shape factors because of the transient part of the solution for pressure. However, approximating the solution with an exponential function, one obtains constant shape factors that can be easily implemented in current dual-porosity reservoir simulators. The approximate shape factors provide good results for systems where the transient behavior of pressure is short (a case commonly encountered in fractured reservoirs).     

Detection of interdependent primary systems using wideband cognitive radios

Cognitive radios (CRs) may be sharing multiple frequency bands with primary systems if the CR is a wideband or an ultra wideband (UWB) system. In that case, the CR should ensure all the coexisting primary systems in these bands are detected before it can start data transmission. In this work, we study the primary system detection performance of a wideband CR assuming that there are multiple coexisting primary systems and that these primary systems may be jointly active. Accordingly, we consider the implementation of energy detection scheme in multiple bands followed by two detection methods: (i) a maximum-a-posteriori (MAP) based detection (i.e., joint detection) that takes into account the statistics of simultaneously operating systems in independent bands and (ii) a Neyman–Pearson (NP) test based detection that optimizes the threshold values independently in each band (i.e., independent detection). For a simpler implementation of the independent detection, we show that the threshold values obtained from joint detection can be used in order to achieve the optimum NP test based independent detection results. In addition to quantifying the gain of joint detection over independent detection in terms of probabilities of false alarm and detection for practical scenarios, we also present the operation capability of CRs in terms of the fractions of time the CR can access the channel without interfering with the primary systems. The results are important for the practical implementation of multiband detection when the primary systems are known to be interdependent.     

A note on adapting methods for continuous global optimization to the discrete case

In this note we show that various branch and bound methods for solving continuous global optimization problems can be readily adapted to the discrete case. As an illustration, we present an algorithm for minimizing a concave function over the integers contained in a compact polyhedron. Computational experience with this algorithm is reported.