Hybrid Energy Research Articles

Hybrid (solar and wind) energy system for Al Hallaniyat Island electrification

Wind–PV–diesel hybrid power generation system technology is a promising energy option since it provides opportunities for developed and developing countries to harness naturally available, inexhaustible and pollution-less resources. The aim of this study is to assess the techno-economic feasibility of utilizing a hybrid wind–PV–diesel power system to meet the load of Al Hallaniyat Island. Hybrid Optimization Model for Electric Renewables software has been employed to carry out the present study. The simulation results indicate that the cost of generating energy (COE) is $0.222 kWh−1 for a hybrid system composed of a 70 kW PV system, 60 kW wind turbine and batteries together with a 324.8 kW diesel system. Moreover, using the same system but without batteries will increase the COE to $0.225 kWh−1, the fuel consumption, the excess energy and the total operating hours for the diesel generators. The PV–wind hybrid option is techno-economically viable for rural electrification.

Thin topological insulator film in a perpendicular magnetic field

We report on a study of an ultrathin topological insulator film with hybridization between the top and bottom surfaces, placed in a quantizing perpendicular magnetic field. We calculate the full Landau-level spectrum of the film as a function of the applied magnetic field and the magnitude of the hybridization matrix element, taking into account both the orbital and the Zeeman spin splitting effects of the field. For an undoped film, we find a quantum phase transition between a state with a zero Hall conductivity and a state with a quantized Hall conductivity equal to ${e}^{2}/h$, as a function of the magnitude of the applied field. The transition is driven by the competition between the Zeeman and the hybridization energies.

Efficient use of accessibility in microRNA target prediction

Considering accessibility of the 3′UTR is believed to increase the precision of microRNA target predictions. We show that, contrary to common belief, ranking by the hybridization energy or by the sum of the opening and hybridization energies, used in currently available algorithms, is not an efficient way to rank predictions. Instead, we describe an algorithm which also considers only the accessible binding sites but which ranks predictions according to over-representation. When compared with experimentally validated and refuted targets in the fruit fly and human, our algorithm shows a remarkable improvement in precision while significantly reducing the computational cost in comparison with other free energy based methods. In the human genome, our algorithm has at least twice higher precision than other methods with their default parameters. In the fruit fly, we find five times more validated targets among the top 500 predictions than other methods with their default parameters. Furthermore, using a common statistical framework we demonstrate explicitly the advantages of using the canonical ensemble instead of using the minimum free energy structure alone. We also find that ‘naïve’ global folding sometimes outperforms the local folding approach.

Accuracy of quasicontinuum approximations near instabilities

The formation and motion of lattice defects such as cracks, dislocations, or grain boundaries, occurs when the lattice configuration loses stability, that is, when an eigenvalue of the Hessian of the lattice energy functional becomes negative. When the atomistic energy is approximated by a hybrid energy that couples atomistic and continuum models, the accuracy of the approximation can only be guaranteed near deformations where both the atomistic energy as well as the hybrid energy are stable. We propose, therefore, that it is essential for the evaluation of the predictive capability of atomistic-to-continuum coupling methods near instabilities that a theoretical analysis be performed, at least for some representative model problems, that determines whether the hybrid energies remain stable up to the onset of instability of the atomistic energy. We formulate a one-dimensional model problem with nearest and next-nearest neighbour interactions and use rigorous analysis, asymptotic methods, and numerical experiments to obtain such sharp stability estimates for the basic conservative quasicontinuum (QC) approximations. Our results show that the consistent quasi-nonlocal QC approximation correctly reproduces the stability of the atomistic system, whereas the inconsistent energy-based QC approximation incorrectly predicts instability at a significantly reduced applied load that we describe by an analytic criterion in terms of the derivatives of the atomistic potential.

First-principles study of the structural and electronic properties of VB 2 under high pressure

We have investigated the structural parameters, elastic constants, electronic properties and ionic configuration of VB 2 under pressure ranging from 0 to100 GPa by plane-wave pseudopotential density functional theory. Our results at zero pressure are in good agreement with the available experimental and other theoretical data. The analyses of the structural parameters and elastic constants of VB 2 versus pressure suggest that this compound is a very stable material under high pressure and the anisotropies of VB 2 will gradually weaken with pressure. Also we present the variation of density of the states (DOS) with applied pressure, and it is found that the density of the states near the Fermi level decreases with pressure, indicating the reduction in the hybridization energy under high pressure. Based on the Mulliken population analysis, we find the charge transferred from V to B increases with pressure.

Effect of Pd doping on the Kondo insulating state in CeRh1−xPdxSb

AbstractIt follows from our analysis that the formation of the Kondo insulator (KI) state in CeRh1−xPdxSb is due to the formation of the collective Kondo singlet state. The semiconducting gap in CeRhSb is strongly reduced with Pd substitution, the activated behaviour in the resistivity is observed only for $x\; < \;0.08$. In this paper, we present a schematic phase diagram for CeRh1−xPdxSb on the temperature T−x plane, based on the magnetic susceptibility data and resistivity. For $x \leq 0.06$ the intra‐atomic hybridization energy V dominates the KI ground state. With increase in x the hybridization V is strongly reduced, which leads to metallic properties of CeRh1−xPdxSb.

Electronic Properties of Nonideal Nanotube Materials: Helical Symmetry Breaking in DNA Hybrids

Helical wrapping of single-strand DNA around single-wall nanotubes (SWNTs) results in the symmetry breaking and modification of the nanotube band structure. Empirical tight-binding theory was employed to investigate this symmetry breaking and modulation of the electronic and optical properties of a SWNT in the field of an ionized DNA. The model allows the computation of the polarization component of the hybrid's energy of cohesion, with a typical value of 0.5 eV per DNA base. A screening parameter that quantifies the response of the SWNT electrons to the DNA perturbation was obtained. SWNT symmetry breaking shows up in the optical absorption for light polarized across the SWNT axis. In addition, circular dichroism is predicted for DNA-SWNT hybrids, even when the nanotube itself is achiral. These optical effects may be used for experimental determination of the DNA wrapping.

Sharp Stability Estimates for the Force-Based Quasicontinuum Approximation of Homogeneous Tensile Deformation

The accuracy of atomistic-to-continuum hybrid methods can be guaranteed only for deformations where the lattice configuration is stable for both the atomistic energy and the hybrid energy. For this reason, a sharp stability analysis of atomistic-to-continuum coupling methods is essential for evaluating their capabilities for predicting the formation of lattice defects. We formulate a simple one-dimensional model problem and give a detailed analysis of the linear stability of the force-based quasicontinuum (QCF) method at homogeneous deformations. The focus of the analysis is the question of whether the QCF method is able to predict a critical load at which fracture occurs. Numerical experiments show that the spectrum of a linearized QCF operator is identical to the spectrum of a linearized energy-based quasi-nonlocal quasicontinuum (QNL) operator, which we know from our previous analyses to be positive below the critical load. However, the QCF operator is nonnormal, and it turns out that it is not generally positive definite, even when all of its eigenvalues are positive. Using a combination of rigorous analysis and numerical experiments, we investigate in detail for which choices of “function spaces” the QCF operator is stable, uniformly in the size of the atomistic system.

DNA codes for additive stem similarity

DNA sequences are sequences with elements from the quaternary DNA alphabet {A, C, G, T}. An important property of them is their directedness and ability to form duplexes as a result of hybridization process, i.e., coalescing two oppositely directed sequences. In biological experiments exploiting this property it is necessary to generate an ensemble of such sequences (DNA codes) consisting of pairs of DNA sequences referred to as Watson-Crick duplexes. Furthermore, for any two words of the DNA code that do not form a Watson-Crick duplex, hybridization energy--stability measure of a potential DNA duplex--is upper bounded by a constant specified by conditions of an experiment. This problem can naturally be interpreted in terms of coding theory. Continuing our previous works, we consider a nonadditive similarity function for two DNA sequences, which most adequately models their hybridization energy. For the maximum cardinality of DNA codes based on this similarity, we establish a Singleton upper bound and present an example of an optimal construction. Using ensembles of DNA codes with special constraints on codewords, which we call Fibonacci ensembles, we obtain a random-coding lower bound on the maximum cardinality of DNA codes under this similarity function.

Reexamining microRNA Site Accessibility in Drosophila: A Population Genomics Study

Kertesz et al. (Nature Genetics 2008) described PITA, a miRNA target prediction algorithm based on hybridization energy and site accessibility. In this note, we used a population genomics approach to reexamine their data and found that the PITA algorithm had lower specificity than methods based on evolutionary conservation at comparable levels of sensitivity.We also showed that deeply conserved miRNAs tend to have stronger hybridization energies to their targets than do other miRNAs. Although PITA had higher specificity in predicting targets than a naïve seed-match method, this signal was primarily due to the use of a single cutoff score for all miRNAs and to the observed correlation between conservation and hybridization energy. Overall, our results clarify the accuracy of different miRNA target prediction algorithms in Drosophila and the role of site accessibility in miRNA target prediction.

Core-level and valence-band study using angle-integrated photoemission onLaFeAsO0.9F0.1

Using angle-integrated photoemission spectroscopy we have probed the novel ${\text{LaFeAsO}}_{0.9}{\text{F}}_{0.1}$ superconductor over a wide range of photon energies and temperatures. We have provided a full characterization of the orbital character of the valence-band (VB) density of states (DOS) and of the magnitude of the $d\text{\ensuremath{-}}p$ hybridization energy. Finally, we have identified two characteristic temperatures: 90 K where a pseudogap-like feature appears to close and 120 K where a sudden change in the DOS near ${E}_{F}$ occurs. We associate these phenomena with the spin density wave magnetic ordering and the structural transition seen in the parent compound, respectively. These results suggest the important role of electron correlation, spin physics, and structural distortion in the physics of Fe-based superconductors.

Enhanced Seismic Performance of Hybrid Bridge Systems: Comparison with Traditional Monolithic Solutions

Remarkable accomplishments have been observed in seismic engineering in the recent past with the definition and development of high-performance seismic resistant systems, able to sustain major ground motions with limited level of structural damage. Following the introduction and further developments of jointed ductile connections for the seismic design of precast concrete buildings, the concept of hybrid system, where self-centering and energy dissipation capacity are adequately combined by using unbonded post-tensioned techniques and alternative sources of dissipation, has been recently proposed as a viable and efficient solution for an improved seismic performance of bridge systems. In this contribution, based on extensive inelastic time-history analyses using a 3-D lumped plasticity model, a numerical comparison of the seismic response of multi-span bridge systems with hybrid jointed ductile and monolithic connections is presented. The seismic performance of the two alternative solutions is evaluated with reference to the different mechanisms developed to accommodate the inelastic demand as well as to the extent of maximum and residual (permanent) displacement or drifts. Parametric analyses are carried out by varying fundamental mechanical and geometric parameters of the bridge systems as: the distribution of pier heights within a regular or irregular configuration, deck stiffness, and abutment restraint conditions. In addition, the influence of P-Δ effects and seismic intensity on the overall response are investigated and reported as a further confirmation of the likely enhanced performance of hybrid bridge systems.

Weld microstructure and shape of laser–arc hybrid welding

A series of CO2 laser–metal inert gas arc hybrid welding experiment was carried out to investigate the effects of laser/arc energy ratio and groove parameters on the shape and microstructure of hybrid weld. The results showed that increasing arc current and groove cross-section area can reduce dimension difference of laser zone and arc zone by enhancing the uniform of energy distribution in molten pool. The arc current can speed the melted metal flow to the pool root and drive more heat to the pool below by the arc pressure, and groove area can reduce the resistance of melted metal flowing to the pool root. The microstructure of hybrid weld is simultaneously determined by the total line energy of hybrid welding and energy ratio of laser/arc (ERLA), and only under the proper or relatively smaller total line energy ERLA has obvious effects on microstructure. Increasing the ERLA can increase the tendency of hybrid weld to obtain structure with higher hardness. Furthermore, the mechanical performance of the hybrid weld with lower ERLA is good.

Toyota Motor Company: An Environmental and Strategic Marketing Assessment for Hybrid and Renewable Energy Resource Automobiles

Toyota Motor Company: An Environmental and Strategic Marketing Assessment for Hybrid and Renewable Energy Resource Automobiles

On the construction of hybrid potential energy functions for the treatment of local anharmonicity in molecular vibrations†

This paper reports a process by which a local, accurate, and intrinsically anharmonic potential function may be joined with a larger harmonic oscillator representation of the remainder of a molecule to build a hybrid potential energy function. Such functions find use in chemical dynamics in which there is local anharmonic bond breaking and forming, but the remainder of the molecular system behaves essentially as a set of harmonic oscillators. In constructing such a potential, for malonaldehyde as an example, it is assumed that the harmonic-limit potential can be found for the system using a given data set of the Cartesian forces and force constants derived with the use of a computational quantum chemistry program. The Pulay transformation is used to establish a set of internal coordinate forces and force constants consistent with the local model potential function. The success (i.e. faithfulness) of the construction of the hybrid potential strongly depends on the choice of internal coordinates. The Pulay transformation together with the vibrational projection analysis of Grafton and Wheeler allows one to see the strengths or weaknesses of particular choices of internal coordinates. †Approved for Public Release. Distribution Unlimited. Dedicated to Péter Pulay on the occasion of the celebration of his scientific achievements: Budapest, 24 May–3 June 2007.

Effect of base mismatch on the electronic properties of DNA–DNA and LNA–DNA double strands: Density-functional theoretical calculations

The electronic properties of double-stranded octametric DNA–DNA and LNA–DNA with a single-base mismatch were compared with those having fully complementary base pairs to quantify the effect of the base mismatch on hybridization energies (HE). A single T-G mismatch in the LNA–DNA gives rise to a significant reduction in HE, which is consistent with a significant lowering of the melting temperature for mismatched LNA–DNA. By contrast, the hybridization strength of the mismatched DNA–DNA depends strongly on local hydrogen-bonding arrangements in the mispaired T-G. The difference in HE is explained in terms of variation in charge distributions around the hydrogen-bonded base pairs.

Gas adsorption on a nanographite ribbon: Hybridization model and simulations

We propose a hybridization model to simulate the gas molecules adsorbed on a single sheet of nanographite ribbon resulting in a conductivity change. In this study, two energy parameters, the chemical and hybridization energies, are employed to simulate and individualize the adsorbed gas. We propose two competing mechanisms, carrier localization and charge distribution, that coexist in the gas adsorption process, which provide a qualitative explanation for the current increase or decrease in gas adsorption experiments. This study gives qualitative information on nanographite ribbons for gas sensor applications.

End-to-end study of the transfer of energy from magnetosheath ion precipitation to the cusp

This paper describes a study of the effects of unstable magnetosheath distributions on the cusp ionosphere. A semi-kinetic model followed by a 2.5D particle-in-cell (PIC) model served as an end-to-end numerical system to study the evolved distributions from precipitation due to reconnection and, then secondly, the energy transfer into the high-latitude ionosphere based on these solar wind/magnetosheath inputs. Using inputs of several representative examples of magnetosheath injections, waves were generated at the lower hybrid frequency and energy transferred to the ionospheric electrons and ions. The resulting wave spectra and ion and electron particle heating was analyzed.

Computer Simulation Study of Molecular Recognition in Model DNA Microarrays

DNA microarrays have been widely adopted by the scientific community for a variety of applications. To improve the performance of microarrays there is a need for a fundamental understanding of the interplay between the various factors that affect microarray sensitivity and specificity. We use lattice Monte Carlo simulations to study the thermodynamics and kinetics of hybridization of single-stranded target genes in solution with complementary probe DNA molecules immobilized on a microarray surface. The target molecules in our system contain 48 segments and the probes tethered on a hard surface contain 8–24 segments. The segments on the probe and target are distinct and each segment represents a sequence of nucleotides (∼11 nucleotides). Each probe segment interacts exclusively with its unique complementary target segment with a single hybridization energy; all other interactions are zero. We examine how the probe length, temperature, or hybridization energy, and the stretch along the target that the probe segments complement, affect the extent of hybridization. For systems containing single probe and single target molecules, we observe that as the probe length increases, the probability of binding all probe segments to the target decreases, implying that the specificity decreases. We observe that probes 12–16 segments (∼132–176 nucleotides) long gave the highest specificity and sensitivity. This agrees with the experimental results obtained by another research group, who found an optimal probe length of 150 nucleotides. As the hybridization energy increases, the longer probes are able to bind all their segments to the target, thus improving their specificity. The hybridization kinetics reveals that the segments at the ends of the probe are most likely to start the hybridization. The segments toward the center of the probe remain bound to the target for a longer time than the segments at the ends of the probe.

Online Synthesis of Diblock Cationic Oligonucleotides for Enhanced Hybridization to their Complementary Sequence

Oligonucleotides are finding an extremely large number of applications in molecular biology and diagnostics, and might become a very selective class of drugs for the treatment of a vast palette of diseases. Oligonucleotides are polyanions that exert their specific activity following hybridization to a complementary sequence borne by another polyanionic nucleic acid. As drug candidates, they must also be capable of crossing the anionic cell membrane. Simple electrostatic considerations imply that hybridization energy and cell binding could benefit from the addition of cationic groups to the oligonucleotide structure. To reach this goal, many synthetic approaches for introducing ammonium or guanidinium residues into oligonucleotides have been explored: phosphate backbone replacement, ribose or nucleic base modification and end conjugation of a polycation. However, hybridization specificity, nucleic acid-processing enzyme activity and metabolite toxicity concerns all point to the diblock approach, in which the polycation is appended to an otherwise natural oligonucleotide, as the best solution. Unfortunately, stepwise automated synthesis of oligonucleotide–cationic peptide conjugates is not yet routine. Unfortunately, conjugation chemistry between preformed large blocks is not straightforward, especially in water, where “super” zwitterions raise intractable solubility, purification and characterization problems. Moreover, molecular biology and diagnostics applications require fast and straightforward synthesis of any given base sequence linked to any ACHTUNGTRENNUNGorganic cation length. With these considerations as guidelines, we have focused our efforts towards developing a high-yield automated synthesis of oligonucleotide–oligocation conjugates that makes exclusively use of classical phosphoramidite chemistry. In addition to the four A-, T-, Gand C-protected trityl phosphoramidite vials, a linear polyamine N-protected trityl phosphoramidite vial was plugged into the oligonucleotide synthetizer machine to allow online, computer-driven, synthesis (Scheme 1). Decamer oligonucleotides bearing a global charge of up to +9 were synthesized in good yield and characterized by ESMS and PAGE. Duplex melting temperature measurements showed that stability increases up to DTm=45 8C for the largest oligocation moiety. In order to avoid potential toxicity of metabolites, the cationic synthon was based on the largest naturally occurring polyamine, namely spermine. Spermine is present at millimolar concentration in cells, and end-alkylation seems harmless. Amine protection followed by a,w-bishydroxylalkylation led to a diol compatible with oligonucleotide synthesis (Scheme 2). Classical dimethoxytrityl (DMT)/phosphoramidite elongation chemistry was implemented together with base-labile trifluoroacetyl (TFA) protecting groups. The spermine synthon 1 was obtained in eight steps with an overall yield of 12%. A series of decamer oligonucleotides of identical sequences N10= CACCGTAGCG appended with increasing numbers of spermine residues S was synthesized on the micromolar scale on an Expedite 8909 oligonucleotide synthetizer. Individual coupling yields were determined by spectrophotometric determination of the total amount of DMT released during each step. For the nucleoside phosphoramidites, typical coupling yields over 97% were obtained under standard conditions, whereas coupling of 1 had to be optimized to finally reach 90– 96% routinely. The synthesis was stopped with the last DMT group remaining on the oligomer to facilitate separation from truncated sequences. Oligomer cleavage from the solid support and full deprotection were performed under standard aqueous ammonia conditions. Oligomers were purified by reversed-phase HPLC or by using a Poly-Pak II cartridge. DMT was removed by using either standard acetic acid conditions or 2% aqueous TFA to give 80–250 nmol decaoligonucleotide– spermine conjugates N10Sn with up to six spermines [a] B. Pons, Dr. M. Kotera, Dr. G. Zuber, Dr. J.-P. Behr Laboratoire de Chimie G!n!tique associ! au C.N.R.S. Universit! Louis Pasteur de Strasbourg, Facult! de Pharmacie B. P. 24, 67401 Illkirch (France) Fax: (+33)390-244-306 E-mail : kotera@bioorga.u-strasbg.fr behr@bioorga.u-strasbg.fr Supporting information for this article is available on the WWW under http://www.chembiochem.org or from the author. Scheme 1. Synthesis of oligonucleotide–oligospermine conjugates NmSn.