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•This study is investigated for hydrogen production using N4 graphene embedded by V metal.•Chemical adsorption is observed on hydrazine interaction with this surface.•The surface is ...more suitable for hydrazine gas sensors because of high adsorption energy.•After adsorption on the surface, the NN bond becomes much weaker.•The activation energy of NN bond cleavages is lower on surfaces than that of NH bond cleavages.•The generation of hydrogen on the V-N4 graphene surface is quite promising for hydrogen generation because the activation energy of NH scissions is 0.89 eV and activation energy of NN cleavage are close to each other.
In this article, the catalytic effect of the VN4 on graphene has been studied for the decomposition of hydrazine (N2H4) with Density Functional Theory (DFT) calculations using DFT-D3 in the method of Grimme. The adsorb energy, a Bader charge transfer, charge density difference, and partial density of states were examined. Hydrazine decomposition is investigated in two different ways; the NN bond cleavage for N2H4→NH2+NH2 reaction and the NH bond cleavage for N2H4→N2H3+H to produce hydrogen production. According to our result, the gauche conformer of hydrazine is the most stable formation on the modified graphene surface. The interaction of hydrazine molecule with the surface is chemical adsorption through adding V impurity. The NN bond split for V embedded surface has lower activation energy than that of the NH bond cleavages. It is promising to investigate hydrogen generation from hydrazine on the high-performance graphene-like catalyst.
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•The carbon incorporation into FeN4 considerably changes the chemical bonding environment of Fe atom.•As more carbons are exchanged with nitrogens, Fe-included chemical bonds become ...more covalent.•Formation energy changes are in linear correlation with average ICOHP values upon carbon incorporation into porphyrin units.•The magnetic behaviour of Fe-embedded graphene is tunable changing the number of dopants N atoms.•The stability on different surfaces can be compared as C2H4 > C2H2 > C2H6 >CH4 on all surfaces.•The charge difference correlates with the adsorption energy when the number of N atoms is alternated in the system of C2H2, and C2H6. The almost linear decrement between Bader charge difference and adsorption energy occurs for the C2H2 molecule along with varying N atoms.•After adding N atoms to the graphene surface, the linear relationship occurs on magnetic momentum change and Bader charge difference on the adsorption mechanism of C2H4. Additionally, the interactions get weaker because of adding N atoms to the graphene sheet.
Hydrocarbons resulting from petrol, natural gas, and biomass penetrated industry and daily life because of energy consumption. Therefore, their adsorption mechanism needs to be detailed for reliable and inexpensive sensor, capture, and gas storage technology. These mechanisms of hydrocarbons (methane CH4, ethane (C2H6), ethylene (C2H4), and acetylene (C2H2) on FeNx(x=2,3,4) embedded graphene surfaces are analyzed. DFT-derived parameters were calculated via Quantum Espresso software using Grimme-D3 Van der Waals (VdW) correction. Our first findings show that the chemical bonding environment of the central Fe atom is compassionate upon carbon atom incorporation into porphyrin units. As more carbon atoms are exchanged with nitrogen atoms, the mean bond strengths between Fe and neighboring atoms increase based on crystal orbital Hamilton population (COHP), crystal orbital bond index (COBI), and Atoms in Molecules (AIM) Bader Topological Analysis. As opposed to that, more carbon atoms in porphyrin units make Cporp-CGrap interactions weakened and more ionic. The relationships between the adsorption components (adsorption energy, amount of the charge transfer, elevation between molecule and surface, and the variation of magnetic moments) are examined. The strong interaction occurs for C2H2 molecule on FeN2 and FeN3, and C2H4 on all sheets. It was also found that the variation in integrated quantities of COHP (ICOHP)/COBI (ICOBI) and AIM-Bader parameters are in line with the adsorption energy variations of all molecules.
This paper presents a new empirical model for single layer drying process, which was verified with selected experimental data. The present model is also compared with other single layer drying models ...available in the literature, using laboratory as well as field data from literature.
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•The strongest interaction is NO2 on CoN4 graphene surface with chemical interaction. The second most stable interaction is NO molecule on CoN2 and CoN3 graphene.•CoN2 graphene gives ...better results for NO, O2, CO,NH3 molecules.•CoNx surfaces are insensitive for CO2 molecule.•There are linear correlations between the parameters of the adsorption system such as.•Adsorption energy and the elevation on CO adsorption mechanism.•Adsorption energy and Bader charge exchange on NO and O2 systems.
The adsorption mechanisms of small gases on CoNx (x = 2,3,4) embedded graphene surfaces are investigated using DFT calculation. Focusing Bader charge analysis, charge density difference, Density of State for surface analysis and partial density of state, the gas activities (CO,CO2,NO,NO2,NH3 and O2) are studied in Quantum Esspresso software with Van der Waals correction. The adsorption energy, charge transfer, gas height from the surfaces, bond lengths, and magnetic momentum are calculated to understand the gas adsorption mechanisms. Doping nitrogen to graphene surface changes the gas adsorption system. Doping/removing nitrogen to/from the surface can increase the stability of gas on the modified graphene sheet. The study exhibits that the most stable gas is NO2 on CoNx graphene with chemical interaction. The weak interactions are observed on NH3 and CO2 molecules. These modified graphene sheets are promising materials as gas sensors.
In this study, complex processes in a typical Electric Arc Furnace (EAF) such as combustion, radiation, heat, and mass transfer were solved and the optimum injector location was found using ...computational fluid dynamics (CFD). The main aim of the injection optimization was to improve the thermal performance and the metallurgical process by changing the injection angle, the central angle of the injector (CAI), and injector length. Fifteen parametric cases were predicted and analyzed for optimization study. To decrease each simulation solution time of each cases, a polyhedral mesh structure was used instead of tetrahedral mesh for the EAF geometry. Thus, the total element number of the model was decreased by 1/5 while providing faster and unchanging results compared to the case with a tetrahedral mesh structure. The response surface optimization method was used for the optimization study. As a result, the optimum injector positioning was obtained as injection angle: -45°, injector length 614 mm, and CAI: 60°.
This paper is concerned with the energy and exergy analyses of the drying process of shelled and unshelled pistachios using a solar drying cabinet. Using the first law of thermodynamics, energy ...analysis was carried to estimate the amounts of energy gained from solar air collectors and the ratios of energy utilization. However, exergy analysis was accomplished to determine the location, type, and magnitude of exergy losses during the solar drying process by applying the second law of thermodynamics. It was deduced that the exergy losses took place mostly in the 15th shelf where the available energy was less utilized. Moreover, the shelled and unshelled pistachios are sufficiently dried in the ranges between 40 and 60 °C and 37 and 62% of relative humidity at 1.23 m s
−1 of drying air velocity in 6 h despite the exergy losses of 0.15–3.08 kJ kg
−1.
Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to ...estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types.
We investigate the characteristics of BSRs, using conventional and high resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface.
Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. The commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.
•Propose that all BSRs are in fact discontinuous in nature.•Challenge the commonly accepted textbook definition of a BSR.•Acquisition geometry and frequency content significantly impact imaging of BSRs.•Frequency content of seismic data is a key factor in characterizing gas hydrates.•Present precise maps of discontinuous BSRs, not just areal extent.
In this article, the catalytic effect of the Ni-embedded graphene has been investigated for hydrazine (N2H4) decomposition reaction through Density Functional Theory (DFT) calculations with Grimme-D2 ...dispersion correction. Nickel embedded graphene systems are expected to be much cheaper than pristine nickel surfaces in the future because of relatively few numbers of Ni atom usage, experimentally synthesizable, and limit the Ni usage. The transformation of N2H4 has been taken into account in two different ways. The first way is sequential N–H and, the second one is the N–N bond cleavage from the gauche conformation which is the most stable conformation in gas phase and sole conformation observed on the Ni site. According to our findings, ·NH2 formation breaking the N–N bond in hydrazine has lower activation energy than hydrogen abstraction from hydrazine. The difficulty of breaking N–H bonds stems from the spatial accumulation of negative and positive charges, so it causes a mismatch between hydrogen atoms and negatively charges carbon atoms. NH3 formation pathway through the interaction of N2Hx (x = 1 → 4) species with co-adsorbed ·NH2 radicals is accompanied by much lower activation barriers and highly exothermic. Nevertheless, metal-embedded graphene systems are promising materials for hydrazine dehydrogenation and can be tailored to have more efficient charge distribution.
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•Hydrazine decomposition has been investigated on Nickel-embedded graphene.•Hydrogen and ammonia generation routes are considered.•N-2p orbitals interacts stronger with Ni-3d than H-1s during hydrazine adsorption.•Hydrogen abstraction occurs easily with ·NH2 radical that generates ammonia.•Spatial distribution of positive and negative charges limits H abstraction.
Although the origin of cardiac syndrome X (CSX) is still debated, endothelial dysfunction leading to reduced coronary microvascular dilatory response and increased coronary resistance is thought to ...have an important role in the pathogenesis. Erectile dysfunction (ED) is associated with risk factors resulting in endotelial dysfunction. Although the relationship between cardiovascular disease and ED has been well established; the relation between CSX and ED has not been extensively studied so far. We herein aimed to study ED in patients with CSX. The study was designed as a prospective case-control study. Blood samples were analyzed with respect to concentrations of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides. The subjects answered the native language five-item version of the International Index of Erectile Function Questionnaire (IIEF)-5. Each question was scored from 0 to 5 with a maximum score of 25 denoting healty subjects. We investigated the IIEF-5 score in 51 men with CSX (mean age=48.2±6.4 years), 53 men with demonstrated coronary artery disease (CAD) (mean age=48.3±4.8 years) and 52 male controls with normal coronary arteries (mean age=47.2±6.0 years). Mean IIEF-5 scores were 19.88±3.07 for CSX group, 18.83±3.31 for CAD group and 21.40±2.94 for control group. IIEF-5 scores in CSX group were found to be significantly lower than the those of control group (P<0.001). There were no significant differences in IIEF-5 scores between CSX and CAD groups (P=0.09). We have shown for the first time that patients with CSX have lower IIEF-5 scores compared with controls with normal coronary angiograms. This study suggests that ED and CSX may be different manifestations of a common underlying vascular pathology and vasculogenic ED is frequently seen in CSX at least as much as in CAD.
Abstract Aim Infectious complications after renal transplantation (RT) are associated with significant morbidity. They continue to be the most frequent cause of mortality. We investigated the ...incidence of infections, the causative pathogens, and risk factors contributing to this complication during the first year. Patients and Methods We included demographic and clinical data of the 124 patients who underwent RT in our hospital from December 2004 to June 2010. for statistical analysis. Results Fifty (40.3%) RT recipients developed 80 episodes of infection: urinary tract (n = 68; 85%), intraabdominal (n = 4; 5%), surgical wound (n = 3; 3.8%), or central venous catheter (n = 3; 4%). Eight (10%) were bacteremic. The most commonly isolated bacteria scene (76/80) was Escherichia coli (n = 43; 56.5%) followed by Klebsiella spp. (n = 10; 13.2%) and Pseudomonas spp. (n = 10; 13.2%). Cytomegalovirus infection was detected in 2 recipients; fungal and mycobacterial infections, in no case. It was noteworthy that 52.8% of E. coli and Klebsiella spp. produced extended-spectrum beta-lactamase. Ninety percent of infections developed within 6 months after transplantation. When we compared infected versus noninfected cases, the presence of a double J catheter was the most significant risk factor ( P = .018; odds ratio OR = 0.234; 95% confidence interval CI = 0.070–0.781). In contrast to the initial years after the start of RT in our hospital the incidence of infection decreased over time together with a decrease number and durations of catheterization ( P = .008; OR = 2.707; 95% CI = 1.292–5.672). Conclusions Urinary tract infections were the predominant problem with most isolates resistant to extended-spectrum antibiotics. Therefore, invasive catheters and prophylactic antibiotics should not be used for longer than necessary and infection control measures implemented to decrease the incidence of infections and bacterial resistance.
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