Transition metal oxides are nowadays one of the most important materials in the manufacture of capacitive electrodes. The most important problems with these materials for applied energy storage ...devices are low specific energy and poor electrical conductivity. In this research nickel ferrite nanoparticles (NiFe2O4) and also hybrid of NiFe2O4/rGO are synthesized by hydrothermal method and characterized by XRD, Raman, and XPS analysis. The amount of porosity and specific surface area is studied by BET analysis as and surface morphology is studied by SEM and TEM. To investigate the effect of adding rGO to NiFe2O4 nanoparticles, from a hybrid electrode superconducting electrochemical tests are performed, including CV, EIS, and charge-discharge. This electrode with a capacitance of 584.63 F/g and capacitance retention of 91% after 2000 consecutive cycles can be a tempting option for supercapacitor applications.
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•Synthesis of NiFe2O4/rGO by the hydrothermal method.•Electrochemical reactions occur during a diffusion-controlled process.•NiFe2O4/rGO shows a great capacitance retention of 91% after 2000 cycles.
Using three 6FDA-based polyimides (6FDA-Durene, 6FDA-Durene/DABA (9/1), 6FDA-Durene/DABA (7/3)) and nano-size zeolitic imidazolate framework-8 (ZIF-8), we have fabricated mixed matrix membranes ...(MMMs) with uniform morphology comprising ZIF-8as high as 40wt% loading by directly mixing as-synthesized ZIF-8 suspension into the polymer solution. Permeability of all gases (CO2, CH4, C3H6, and C3H8) increases rapidly with an increase in ZIF-8 loading. However, the addition of ZIF-8 nano-particles into the polymer matrix increases the ideal CO2/CH4 selectivity of only 6.87%, while the ideal C3H6/C3H8 selectivity improves 134% from 11.68 to 27.38 for the MMM made of 6FDA-Durene/DABA (9/1) and 40wt% ZIF-8. Experimental data show that the plasticization resistance and gas pair selectivity of MMMs are strongly dependent on the amount of cross-linkable moiety and annealing temperature. MMMs made of 6FDA-Durene do not show considerable improvements on resistance against CO2-induced plasticization after annealing at 200–400°C, while MMMs synthesized from cross-linkable co-polyimides (6FDA-Durene/DABA (9/1) and 6FDA-Durene/DABA (7/3)) show significant enhancements in CO2/CH4 and C3H6/C3H8 selectivity as well as plasticization suppression characteristics up to a CO2 pressure of 30atm after annealing at 400°C due to the cross-linking reaction of the carboxyl acid (COOH) in the DABA moiety. The MMM made of 6FDA-Durene/DABA (9/1) and 40wt% ZIF-8 possess a notable ideal C3H6/C3H8 selectivity of 27.38 and a remarkable C3H6 permeability of 47.3 Barrer. After thermally annealed at 400°C, the MMM made of 6FDA-Durene/DABA (9/1) and 20wt% ZIF-8 shows a CO2/CH4 selectivity of 19.61 and an impressive CO2 permeability 728 Barrer in mixed gas tests. The newly developed MMMs may have great potential for industrial nature gas purification and C3H6/C3H8 separation.
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•Cross-linkable co-polyimide/ZIF-8 mixed matrix membranes (MMMs) are fabricated.•Effects of diamine ratio on polymer structure and gas separation performance are studied.•Effect of heat treatment temperature on MMM performance is investigated.•Increasing ZIF-8 loading leads to increase MMM permeability for all gasses.•Cross-linkable co-polyimides thermally treated at 400°C have shown selectivity enhancement.
A series of copper/nitrosoarene complexes was created that mimics several steps in biomimetic O2 activation by copper(I). The reaction of the copper(I) complex of ...N,N,N′,N′-tetramethypropylenediamine with a series of para-substituted nitrosobenzene derivatives leads to adducts in which the nitrosoarene (ArNO) is reduced by zero, one, or two electrons, akin to the isovalent species dioxygen, superoxide, and peroxide, respectively. The geometric and electronic structures of these adducts were characterized by means of X-ray diffraction, vibrational analysis, ultraviolet–visible spectroscopy, NMR, electrochemistry, and density functional theory (DFT) calculations. The bonding mode of the NO moiety depends on the oxidation state of the ArNO moiety: κN for ArNO, mononuclear η2-NO and dinuclear μ-η2:η1 for ArNO•–, and dinuclear μ-η2:η2 for ArNO2–. 15N isotopic labeling confirms the reduction state by measuring the NO stretching frequency (1392 cm–1 for κN-ArNO, 1226 cm–1 for η2-ArNO•–, 1133 cm–1 for dinuclear μ-η2:η1-ArNO•–, and 875 cm–1 for dinuclear μ-η2:η2 for ArNO2–). The 15N NMR signal disappears for the ArNO•– species, establishing a unique diagnostic for the radical state. Electrochemical studies indicate reduction waves that are consistent with one-electron reduction of the adducts and are compared with studies performed on Cu-O2 analogues. DFT calculations were undertaken to confirm our experimental findings, notably to establish the nature of the charge-transfer transitions responsible for the intense green color of the complexes. In fine, this family of complexes is unique in that it walks through three redox states of the ArNO moiety while keeping the metal and its supporting ligand the same. This work provides snapshots of the reactivity of the toxic nitrosoarene molecules with the biologically relevant Cu(I) ion.
Probabilistic amplitude shaping (PAS) is a practical means to achieve a shaping gain in optical fiber communication. However, PAS and shaping in general also affect the signal-dependent generation of ...nonlinear interference. This provides an opportunity for nonlinearity mitigation through PAS, which is also referred to as a nonlinear shaping gain. In this paper, we introduce a linear lowpass filter model that relates transmitted symbol-energy sequences and nonlinear distortion experienced in an optical fiber channel. Based on this model, we conduct a nonlinearity analysis of PAS with respect to shaping blocklength and mapping strategy. Our model explains results and relationships found in literature and can be used as a design tool for PAS with improved nonlinearity tolerance. We use the model to introduce a new metric for PAS with sequence selection. We perform simulations of selection-based PAS with various amplitude shapers and mapping strategies to demonstrate the effectiveness of the new metric in different optical fiber system scenarios.
Controlling product selectivity during the catalytic aerobic oxidation of phenols remains a significant challenge that hinders reaction development. This work provides a mechanistic picture of a ...Cu-catalyzed, aerobic functionalization of phenols that is selective for phenoxy-coupled ortho-quinones. We show that the immediate product of the reaction is a Cu(II)–semiquinone radical complex and reveal that ortho-oxygenation precedes oxidative coupling. This complex is the resting state of the Cu catalyst during turnover at room temperature. A mechanistic study of the formation of this complex at low temperatures demonstrates that the oxygenation pathway mimics the dinuclear Cu enzyme tyrosinase by involving a dinuclear side-on peroxodicopper(II) oxidant. Unlike the enzyme, however, the rate-limiting step of the ortho-oxygenation reaction is the self-assembly of the oxidant from Cu(I) and O2. We provide details for all steps in the cycle and demonstrate that turnover is contingent upon proton-transfer events that are mediated by a slight excess of ligand. Finally, our knowledge of the reaction mechanism can be leveraged to diversify the reaction outcome. Thus, uncoupled ortho-quinones are favored in polar, coordinating media, highlighting unusually high levels of chemoselectivity for a catalytic aerobic oxidation of a phenol.
•The visual evaluation of soil structure (VESS) indicated poorer soil structure under conventional tillage compared to minimum tillage.•The VESS result was confirmed by measured soil properties.•VESS ...was not able to differentiate the effects of crop rotation on soil structural quality.•VESS is suitable for rapid evaluation of soil surface structural quality on arable farms.
Conventional methods for assessing soil quality under different management practices require considerable time and knowledge. A visual method based on field assessment can provide a reliable, rapid evaluation of soil quality. The aim of this study was to use the visual evaluation of soil structure (VESS) method in arable soil in Ireland and to assess the ability of the method for evaluating soil structural quality under different arable management systems. The study was conducted over twenty sites used with conventional and minimum tillage, with crop rotation or mono-cropped. At each site a VESS score and soil properties associated with soil structural quality were measured in order to assess the visual soil quality score (Sq). Sq for conventional management (Sq=2.29) was significantly greater than minimum tillage (Sq=1.95) indicating slightly poorer structure. Measured soil parameters confirmed a negative effect of conventional tillage on soil quality and supported the VESS results. Under minimum tillage Sq indicated significantly different soil structure under mono-cropping (Sq=1.66) compared to rotation (Sq=2.06), but this trend was not supported by the other soil properties and the difference probably had no physical meaning as both Sq scores indicated good soil structure. The effects of crop management on soil structure could not be differentiated by VESS under conventional tillage, while the measured soil properties suggested soil structural quality was better under crop rotation. While visual Sq scores were not strongly correlated with individual soil properties indicative of soil quality, Sq scores were generally supported by the measured soil properties with regard to differentiation of tillage system. This independent evaluation of the VESS method on arable farms in Ireland indicated that it was capable of differentiating the effects of tillage management practices on soil structural quality, and is suitable for use as a reliable, rapid method for assessing soil quality on arable farms.
Molecular p‐dopants designed to undergo electron transfer with organic semiconductors are typically planar molecules with high electron affinity. However, their planarity can promote the formation of ...ground‐state charge transfer complexes with the semiconductor host and results in fractional instead of integer charge transfer, which is highly detrimental to doping efficiency. Here, we show this process can be readily overcome by targeted dopant design exploiting steric hindrance. To this end, we synthesize and characterize the remarkably stable p‐dopant 2,2′,2′′‐(cyclopropane‐1,2,3‐triylidene)tris(2‐(perfluorophenyl)acetonitrile) comprising pendant functional groups that sterically shield its central core while retaining high electron affinity. Finally, we demonstrate it outperforms a planar dopant of identical electron affinity and increases the thin film conductivity by up to an order of magnitude. We believe exploiting steric hindrance represents a promising design strategy towards molecular dopants of enhanced doping efficiency.
Integer charge transfer in the p‐doping of organic semiconductors can be suppressed by intermolecular hybridization reducing the doping efficiency. We test the hypothesis that steric hindrance can be exploited to inhibit this process for a novel three‐dimensional dopant whose doping behavior is contrasted with an equally strong planar species. We find that utilizing steric hindrance in dopant design indeed promotes integer charge transfer.
Performance of tractor and tillage implements in clay soil Ranjbarian, Saeed; Askari, Mohammad; Jannatkhah, Javad
Journal of the Saudi Society of Agricultural Sciences,
April 2017, 2017-04-00, 2017-04-01, Letnik:
16, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A mobile instrumentation system was developed and mounted on an MF 285 tractor to measure the performance parameters of the tractor and attached implements. The system measures implement draft, fuel ...consumption, real forward velocity, tillage depth and engine speed. Other parameters such as wheel slippage, drawbar power and traction efficiency would be calculated by ASABE standard. Overall energy efficiency for the tractor-implement system was calculated, too. Three implements included of moldboard plow, disk plow and chisel plow at four forward velocities (1.5, 2.3, 3 and 4km/h) in 23cm depth and 1500rpm engine speed was examined. Analysis of variance (ANOVA) of resulted data revealed that increase of forward velocity results in increase of implement draft, wheel slippage, drawbar power and overall energy efficiency but results in decrease of traction efficiency. Furthermore, fuel consumption decreased by increase of velocity from 1.5km/h to 3km/h but increased by increase of velocity from 3km/h to 4km/h. Moreover, it was observed that draft requirement for implements in tests ranged from 8.2kN for the disk plow to 13kN for the chisel plow and fuel consumption ranged from 10.72L/ha for the chisel plow to 26.5L/ha for the moldboard plow. The ranges in mentioned parameters indicate that energy saving can be readily done by selecting energy-efficient implements and by proper matching of the tractor size and operating parameters to the implements.
Among the various transport models for gas separation via membrane, the best description is done by solution-diffusion model. The main parameters of this model are the sorption and diffusion of the ...penetrant through the membrane. Studies conducted by various researchers in the field of gas separation indicate that the thermodynamic interaction (sorption effects) in glassy polymers has the major role in the diffusivity, permeability, and selectivity of the membrane, especially in the multi-component gas mixture. In glassy polymers, dual-mode sorption model is frequently used to describe the equilibrium sorption behavior of a polymer-gas system and, based on this sorption model; the permeation behavior is described by the partial immobilization model. In this study, the difference between the sorption mechanism of CO2 and CH4 in glassy polymeric membranes was analyzed by separating the sorption mode and introducing P50/50 parameter (the pressure at which the contribution of both Henry and Langmuir sorption is equal), which was done using the available experimental data in the scientific references for the sorption values of CO2 and CH4. The contribution of the sorbed molecules in Henry and Langmuir sites was investigated and its changes with pressure were evaluated for CO2 and CH4 permeation. This study was also attempted to provide a correct definition of F factor, used in references, in the form of the multiplication of mobile concentration ratios (CHmobile/CH) by the diffusivity coefficients in two modes (DH/DD).
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