A comparative study on performance and reliability of 32-bit binary adders

In this paper, the performance and reliability of different binary adder families are studied for both the superthreshold and the near-threshold regions of operation. The adder structures are selected from both the carry propagate adders (CPAs) and parallel prefix adders (PPAs). The performance parameters which are used in the comparative study include delay, power, energy, and energy-delay-product (EDP) of the adders. Additionally, the impacts of the process variation and negative bias temperature instability (NBTI) on the delays of the adders under the aggressive supply voltage scaling are investigated. Also, the efficacies of the adders are compared using a merit function based on their performance and reliability parameters for a wide range of supply voltage levels, from the nominal voltage down to the near-threshold voltage. The study is performed for the 32-bit adder structures designed based on the 14-nm FinFET and 45-nm bulk CMOS technologies. The results which are obtained using HSPICE simulations, reveal that the reliability parameters similar to the performance parameters are a function of the adder architectures and those are the key components to determine the efficiencies of the adders. Also, the results show that the impacts of the process variation and NBTI on the delays of the high performance PPA structures are more than those of the CPA structures for the whole range of the supply voltage. The PPAs, however, have the higher merit factors compared to the CPAs under a wide range of supply voltage levels. The results presented in this paper may provide some guidelines for the designers to select proper adder structures based on their design requirements and constraints.     

Charge transfer complexes between 4,4′-disubstituted diphenyldiacetylenes: experimental and theoretical study

Novel charge transfer (CT) complexes containing donor and acceptor derivatives of diphenyldiacetylene have been synthesised and characterised. The structure of CT complexes was modelled at the B3LYP/6-31G(d)//B3LYP/6-31G(d) level of theory. It was found that the complex formation is mainly due to dipole–dipole interaction between side groups of diacetylene molecules and there was no significant charge transfer between donor and acceptor in the ground state. On the other hand, optical excitation of CT complexes leads to strong charge transfer from donor to acceptor molecule as followed from the modelling using time-dependent density functional theory (DFT) method. Diacetylene molecules adopt strongly bent configuration in CT complexes which is prohibitive for solid-state topochemical polymerisation of diacetylenes     

Evaluation of trap creation and charging in thin SiO2 using both SCM and C-AFM

Conductive atomic force microscopy (C-AFM) and scanning capacitance microscopy (SCM) are used in this work to characterize trap creation and charge trapping in ultra-thin SiO₂. It is found that C-AFM working at normal operational voltages causes severe damage and subsequent negative charge trapping in the oxide. Permanent hillocks are seen in the topography of stressed regions. The height of these features is determined rather by the applied voltage than the electric field. Electrostatic repulsion between tip and sample and Si epitaxy underneath the oxide are the two most probable causes of this feature. The immediate physical damage caused in the oxide during high field C-AFM measurements is a possible showstopper for use of the C-AFM to investigate differences in pristine interface states. SCM operates at lower voltages, yielding less oxide damage and is able to indicate the interface state density variations through hysteresis in the dC/dV vs. V curves.     

Use of neural network method to characterize pressure controlled charge density of silicon nitride films deposited by PECVD

A prediction model of charge density of silicon nitride (SiN) films was constructed by using a generalized regression neural network (GRNN). The SiN film was deposited by a plasma enhanced chemical vapor deposition (PECVD) system and the deposition process was characterized by means of a statistical experiment. The prediction performance of GRNN was optimized by using a genetic algorithm (GA) and yielded an improved prediction of about 63% over statistical regression model. The optimized model was utilized to qualitatively investigate the effect of process parameters under various pressures. A refractive index model was effectively utilized to validate charge density variations. For the variations in process parameters, charge density was strongly dependent on [N-H]. Effects of NH₃ or SiH₄ flow rates were significant only under high collision rate. Effect of pressure-induced collision rate was noticeable only at higher NH₃ flow rate or lower SiH₄ flow rate.     

On solutions of Coulomb system and its generalization to the Aharonov-Bohm effect

The paper numerically analyzes the Aharonov-Bohm effect of an infinitely thin magnetic flux for its influence on a two- or three-dimensional (3d) solutions of Coulomb system in momentum and coordinate spaces. For any definitive eigenstate, it is shown that the flux shifts the position of the most probable radius (MPR) of a probability distribution inward or outward in momentum or coordinate spaces, respectively. Moreover, the probability density of the shifted MPR is amplified in the momentum space, while reduced in the coordinate space. Since the Coulomb force among charged particles dominate the structure of matter, shifting of the MPR controlling by the flux effect may be beneficial to the construction of nanostructure by manipulating the atomic and molecular bonds.     

Kinetic study of cell disruption by ionic polymers with varied charge density

The effect of charge density and hydrophobicity of the polymeric cations on cell disruption is studied thermodynamically and kinetically by using the budding yeast protoplast. It is found that cationic polymers drastically disrupt the cells above a certain concentration while nonionic and anionic ones do not. Reduced charge density of copolymers of cationic and nonionic monomers resulted in decreased cell disruption. However, it is further experimentally proved that the disruption of the cells occurs only when the polycation has a certain hydrophobicity. The stronger the hydrophobicity of the cationic polymer, the more cooperatively the cells are disrupted. Received: 29 May 2000 Accepted: 1 September 2000     

Mechanochemical and Size Reduction Machines for Biorefining

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.     

Conductance Mechanism in a Linear Non-Conjugated Trimethylsilyl-Acetylene Molecule: Tunneling Through Localized States

The conductance properties of 1,3-(trimethylsilyl)-1-tridecene-6,12-diyne, a non-conjugated trimethylsil-acetylene molecule have been investigated both experimentally and theoretically. Based on scanning tunnelling spectroscopy experiments, a discussion on the mechanisms controlling the charge transfer through this linear molecule is carried out. A specific property of the studied molecule is that it contains localized molecular orbitals. The shifts of the MOs energy levels caused by the applied voltage as well as a distant superexchange coupling between the respective localized MOs are shown to become determining in the formation of a nonlinear hole current through the molecule.     

Concerning the regularity of the anisotropic porous medium equation

We show that a locally bounded nonnegative weak solution of the anisotropic porous media equation is locally continuous. The proof is based on DiBenedetto's technique called intrinsic scaling; by choosing an appropriate geometry one can deduce energy and logarithmic estimates from which one can implement an iterative method to obtain the regularity result.