Algebraic Methods for Optimizing Constant Multiplications in Linear Systems

Constant multiplications can be efficiently implemented in hardware by converting them into a sequence of nested additions and shift operations. They can be optimized further by finding common subexpressions among these operations. In this work, we present algebraic methods for eliminating common subexpressions. Algebraic techniques are established in multi-level logic synthesis for the minimization of the number of literals and hence gates to implement Boolean logic. In this work we use the concepts of two of these methods, namely rectangle covering and fast extract (FX) and adapt them to the problem of optimizing linear arithmetic expressions. The main advantage of using such methods is that we can optimize systems consisting of multiple variables, which is not possible using the conventional optimization techniques. Our optimizations are aimed at reducing the area and power consumption of the hardware, and experimental results show up to 30.3% improvement in the number of operations over conventional techniques. Synthesis and simulation results show up to 30% area reduction and up to 27% power reduction. We also modified our algorithm to perform delay aware optimization, where we perform common subexpression elimination such that the delay is not exceeded beyond a particular value.

Jammer target discrimination based on local variance of signal histogram in tracking radar and its implementation

In this article, the effects of the number of quantization levels and the sampled signal are considered in the airborne digital radio frequency memory (DRFM). A different model of analog-to-digital conversion is proposed. The histogram of the proposed model is utilized to release synchronization of signals for integration. Then, the local variance technique is used to highlight the differences between a continuous signal and the sampled pre-quantized DRFM signal. Furthermore, the effects of analog reconstruction filter on a DRFM signal are considered. Simulation results show the efficiency and robustness of the proposed method. Finally, a hardware implementation is provided to prove the proposed method.     

Examination of Relationship Between Mercury Rate with Zinc and Copper Changes in Muscle Tissue of <Emphasis Type="Italic">Otolithes Rubber</Emphasis> in Mahshahr Port—the Persian Gulf

The current study was conducted with the aim of examination of changes scope as well as correlation between mercury with zinc and copper in the muscle tissue of tigertooth croaker as one of the most consumed fish in the area (Mahshahr Port) and its comparison with available standards. The obtained results suggested that, total average concentration of Hg, Zn and Cu (mean ± SE) accumulated in the muscle tissue of tigertooth croaker (Otolithes rubber) are respectively equal to 1426 ± 113; 15999 ± 1045 and 2279 ± 94 (ngg^–1) in summer as well as 955 ± 91; 13172893 and 1678 ± 178 (ngg^–1) in winter. Comparison among accumulation rate of elements Hg, Cu and Zn in two seasons showed a significant correlation between two mentioned seasons for Zn and Hg. The correlation result indicates a positive significant relationship between zinc and copper and a descending significant relationship between Hg with Cu and Zn. Concentration of total mercury accumulated in the muscle tissue of tigertooth croaker (Otolithes rubber) within two seasons, summer and winter, are lower than standard limit (500 ngg^–1) defined by WHO while it is higher than standard limit (300 ngg^–1) estimated by USEPA. Due to high concentrations of Hg, the results can be a serious warning for consumption of this fish in Mahshahr region.     

Progress on Electrospun Composite Fibers Incorporating Bioactive Glass: An Overview

Electrospinning is a promising approach for the development of fibrous tissue engineering (TE) scaffolds suitable for hard and soft tissues. Apart from physicomechanical properties, electrospun fibers are required to incorporate bioactive cues to control cellular functions, including facilitating biomineralization and osteogenic differentiation in case of bone TE, as well as vascularization, to support successful tissue regeneration. In recent years, bioactive glass (BG) addition to electrospun biopolymer fibers has shown promising results in enhancing the properties of fibers, including the improvement of biological performance. In this article, a comprehensive overview of BG-containing electrospun polymer composite fibers is presented, identifying the parameters that affect the mechanical properties as well as the biological response in vivo and in vitro. Subsequently, the effects of BG addition on the properties of the scaffolds are discussed. Recent developments in the fields of bone regeneration, wound healing, and drug delivery using BG-containing electrospun fibrous scaffolds are described in detail. Essential aspects related to BG-polymer composite fibers for translational research in TE are highlighted for future research in this field.     

Cold heavy oil production with sand simulation including wormhole propagation and foamy oil behaviour

Cold heavy oil production with sand (CHOPS) is a primary production method used for heavy oil reservoirs with no requirements of external energy consumption. A new model for CHOPS is simulated by incorporating wormhole propagation and foamy oil behaviour mechanisms to evaluate the recovery of an extra-heavy oil reservoir of the Athabasca region. The most critical mechanisms of CHOPS, wormhole propagation and foamy oil behaviour, are captured by using Wang's model for wormhole propagation and Uddin's model of gas exsolution. After 120 months of simulation, 53.38%, 99.76%, and 100% of wormhole propagation were achieved during three time steps of 12, 48, and 60 months, respectively, toward the sides of the studied reservoir section. The propagation was achieved within all directions of the investigated section compatible with the erratic nature of wormhole propagation. Furthermore, the application of Uddin's model was incorporated into production by reducing the fluid viscosity as a result of the foamy oil behaviour. Over 3% of the recovery was achieved at the end of the primary CHOPS phase simulation by taking into account that we modelled the recovery based on highly viscous oil with API 7.5. Finally, the model can provide an improved understanding of the primary CHOPS process by considering its two significant mechanisms.     

Surface modification of MWCNT to improve the mechanical and thermal properties of natural rubber nanocomposites

In this study, we focused on the synergistic effect between carbon black (CB) and multiwall carbon nanotube (MWCNT) hybrid fillers. In particular, the surface modification of pristine MWCNT (P-MWCNT) via an acid (oxidation) treatment was used to improve their dispersion, as well as the mechanical and thermal properties of their corresponding natural rubber (NR)-based nanocomposites. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were carried out to determine the presence of functional groups on the oxidized MWCNT (O-MWCNT). After vulcanization, dynamic mechanical analysis (DMA), tensile properties, hardness, thermal conductivity, swelling behaviour in toluene and SEM characterizations were performed on both NR/CB/P-MWCNT- and NR/CB/O-MWCNT-based nanocomposites. The results showed the positive effect of MWCNT surface oxidation on the fillers' dispersion and nanocomposites' properties.     

Gradient Type-II CdSe/CdSeTe/CdTe Core/Crown/Crown Heteronanoplatelets with Asymmetric Shape and Disproportional Excitonic Properties

Characterized by their strong 1D confinement and long-lifetime red-shifted emission spectra, colloidal nanoplatelets (NPLs) with type-II electronic structure provide an exciting ground to design complex heterostructures with remarkable properties. This work demonstrates the synthesis and optical characterization of CdSe/CdSeTe/CdTe core/crown/crown NPLs having a step-wise gradient electronic structure and disproportional wavefunction distribution, in which the excitonic properties of the electron and hole can be finely tuned through adjusting the geometry of the intermediate crown. The first crown with staggered configuration gives rise to a series of direct and indirect transition channels that activation/deactivation of each channel is possible through wavefunction engineering. Moreover, these NPLs allow for switching between active channels with temperature, where lattice contraction directly affects the electron–hole (e–h) overlap. Dominated by the indirect transition channels over direct transitions, the lifetime of the NPLs starts to increase at 9 K, indicative of low dark-bright exciton splitting energy. The charge transfer states from the two type-II interfaces promote a large number of indirect transitions, which effectively increase the absorption of low-energy photons critical for nonlinear properties. As a result, these NPLs demonstrate exceptionally high two-photon absorption cross-sections with the highest value of 12.9 × 10⁶ GM and superlinear behavior.