Computational study on the reaction mechanism of atmospheric oxidation of ethanol with ozone

The reaction of C₂H₅OH and O₃ on the singlet potential energy surface is carried out using the MP2 and CCSD(T)//MP2 theoretical approaches in connection with the 6-311++G(d,p) basis set. Three pre-reactive complexes C1, C2, and C3 are formed between ethanol and ozone at atmospheric pressure and 298.15 K temperature. With variety of the complexes, seven types of product are obtained which four types of them have enough thermodynamic stability. In thermodynamic approach, the most favor product begins with the formation of pre-reactive C2 complex and produces the CH₃CH(OH)₂ + O₂ as final adduct in a process that is computed to be exothermic by ?53.759 kcal/mol and spontaneous reaction by ?51.833 kcal/mol in Gibbs free energy. In kinetic viewpoint, the formation of CH₃COH + cis-H₂O₃ as a final adducts is the most favor path.     

A delay model and optimization method of a low-power BiCMOS logiccircuit

A new delay model and optimization method is proposed for a low-power BiCMOS driver. A transient overdrive, base directly-tied complementary BiCMOS logic circuit operates faster than conventional BiCMOS and CMOS circuits for supply voltage down to 1.5 V by using a speed-power-area optimization approach. An analytical delay expression is derived for the first time for a full-swing BiCMOS circuit with short-channel effects. The circuit is simulated with a HSPICE model using 0.8-μm BiCMOS technology with a 6-GHz n-p-n and a 1-GHz p-n-p transistor. The simulation results have verified the analytical results and demonstrated that the circuit can work up to 200 MHz operating frequency for a load capacitance of 1 pF at 1.5 V of supply voltage     

A versatile time-domain Reed-Solomon decoder

A versatile Reed-Solomon (RS) decoder structure based on the time-domain decoding algorithm (transform decoding without transforms) is developed. The algorithm is restructured, and a method is given to decode any RS code generated by any generator polynomial. The main advantage of the decoder structure is its versatility, that is, it can be programmed to decode any Reed-Solomon code defined in Galois field (GF) 2^m with a fixed symbol size m. This decoder can correct errors and erasures for any RS code, including shortened and singly extended codes. It is shown that the decoder has a very simple structure and can be used to design high-speed single-chip VLSI decoders. As an example, a gate-array-based programmable RS decoder is implemented on a single chip. This decoder chip can decode any RS code defined in GF (2⁵) with any code word length and any number of information symbols. The decoder chip is fabricated using low-power 1.5-μ, two-layer-metal, HCMOS technology     

Modification of the Peng–Robinson equation of state for helium in low temperature regions

Helium shows the nearest behaviour to ideal gas in the room conditions. In contrast, thermodynamic behaviour of helium in the critical region, in which its liquefaction is possible, is extremely complicated. The equation of state (EOS), which is in common use for helium, is the modified Benedict–Webb–Rubin (MBWR) EOS developed by McCarty and Arp which is a 13th-order equation with 32 substance-dependent parameters. MBWR is a complicated EOS and its use is time consuming. In this work, the modified Peng–Robinson EOS introduced by Feyzi et al. is customised with 10 adjustable parameters for helium in the temperature range of 2.20–15.20 K and pressures up to 16 bar. The proposed EOS is able to predict the properties of helium in the vapour–liquid equilibrium (VLE) conditions and in the single gas-phase region. In addition, a temperature-dependent correlation for constant pressure heat capacity of helium from very low up to normal temperatures is proposed. The liquefaction process of helium, which is being done by cooling it to very low temperatures by passing through a Joule–Thomson valve, is predicted by the proposed EOS. Very accurate results are observed.     

Distance-based-decoding of block turbo codes

List-based algorithms for. decoding block turbo Codes (BTC) have gained popularity due to their low computational complexity. The normal way to calculate the soft outputs involves searching for a decision code word D and a competing codeword B. In addition, a scaling factor /spl alpha/ and an estimated reliability value /spl beta/ are used. In this letter, we present a new approach that does not require /spl alpha/ and /spl beta/. Soft outputs are generated based on the Euclidean distance property of decision code words. By using the new algorithm, we achieve better error performance with even less complexity-for certain BTCs.     

Synthesis of high specific surface area YSZ (ZrO<Subscript>2</Subscript>–8Y<Subscript>2</Subscript>O<Subscript>3</Subscript>) nanocrystalline powder by modified polymerized complex method

In this study high specific surface area yttria-stabilized zirconia (ZrO₂–8Y₂O₃) nanocrystalline powder have been synthesized through “modified polymerized complex (MPC) method”. Zirconium chloride, yttrium nitrate, citric acid and ethylene glycol were polymerized at 80 °C to produce a gel-like mass in which metallic ions were uniformly distributed. During the thermal treatment of dried gel, nanocrystalline YSZ powder was formed. Thermal reactions and phase formation of dried gel were investigated through thermal analysis (DTA/TG) and X-ray diffraction (XRD) analysis, respectively. Chemical bonding and thermal decomposition behavior of dried gel was investigated by FTIR analysis. During decomposition, the nature of the bonding between carboxylate groups and the cations changed from unidentate to bridging at 370 °C and carbonate species were detected at 470 °C. Morphology of powder calcined at 650 °C was analyzed by scanning electron microscope (SEM). YSZ powder with high specific surface area was prepared successfully by this method.     

Computational mechanistic study of methanol and molecular oxygen reaction on the triplet and singlet potential energy surfaces

The reaction of CH₃OH with the O₂ on the triplet and singlet potential energy surfaces (PES) was carried out using the B3LYP, MP2, and CCSD(T)//B3LYP theoretical approaches in connection with the 6-311++G(3df–3pd) basis set. Three pre-reactive complexes, ¹C1, ¹C2, and ³C1, on the singlet and triplet PES were formed between methanol and molecular oxygen. From a variety of the complexes, seven types of products are obtained, of which four types are found to be thermodynamically stable. Results reveal that there exists one intersystem crossing between triplet and singlet PES. For P4 adduct that is the main and kinetically the most favorable product, the rate constants are calculated in the temperature range of 200–1,000 K in the reliable pathway.     

Diradical Organic One‐Dimensional Polymers Synthesized on a Metallic Surface

We report on the synthesis and characterization of atomically precise one‐dimensional diradical peripentacene polymers on a Au(111) surface. By means of high‐resolution scanning probe microscopy complemented by theoretical simulations, we provide evidence of their magnetic properties, which arise from the presence of two unpaired spins at their termini. Additionally, we probe a transition of their magnetic properties related to the length of the polymer. Peripentacene dimers exhibit an antiferromagnetic (S=0) singlet ground state. They are characterized by singlet–triplet spin‐flip inelastic excitations with an effective exchange coupling (J_eff) of 2.5 meV, whereas trimers and longer peripentacene polymers reveal a paramagnetic nature and feature Kondo fingerprints at each terminus due to the unpaired spin. Our work provides access to the precise fabrication of polymers featuring diradical character which are potentially useful in carbon‐based optoelectronics and spintronics.     

Analysis of BiCMOS buffer for input voltages with finite rise time

A BiCMOS digital logic gate is analyzed for input voltages with a finite rise or fall time. A new gate delay model to account for the input slope is developed. A set of accurate yet simple closed-form delay expressions are derived for the first time in terms of the input signal slew rate as well as circuit and device parameters. SPICE simulations are used to verify the accuracy of the analytical delay model. The BiCMOS circuit is characterized in terms of the input slew rate, the fan-in, fan-out, and the circuit delay constants. The model can be incorporated in timing simulators and timing analyzers for BiCMOS ULSI circuit design