The oxygen deficient Ruddlesden–Popper La3Ni2O7−δ (δ = 0.65) phase: Structure and properties

La₃Ni₂O_7−δ (δ = 0.65) was synthesized by hydrogen reduction of the parent La₃Ni₂O₇ Ruddlesden–Popper nickelate. The crystal structure of La₃Ni₂O_6.35 (space group: I4/mmm, a = 3.8742 (1) Å and c = 20.055 (1) Å) has been determined from powder neutron diffraction data by the Rietveld method for the first time. The oxygen vacancies are located in the LaO_x planes between two of the NiO₂ layers. Removal of these oxygen atoms from the parent phase results in a significant (∼0.4 Å) shrinkage of the perovskite block along c-direction and splitting of the Ni position. The major part of Ni cations is surrounded by five oxygen atoms forming square pyramids, while the rest are coordinated to six octahedrally arranged oxygen atoms. Over the 170–400 K temperature range, the conductivity of La₃Ni₂O_6.35 follows Mott's variable range hopping model modified for a 2D case.     

Mo-doped Co9S8 nanorod array as a high performance electrochemical water splitting catalyst in alkaline solution

It is very important to exploit robust electrocatalysts for the water splitting in an alkaline medium. Hence, a series of Mo-doped Co₉S₈ nanorod array on Ni foam (Mo–Co₉S₈/NF) was successfully synthesized through hydrotherma and sulfuration processes for the first time and used as an efficient and stable difunctional electrocatalyst for the overall water splitting. Such Mo–Co₉S₈-3//Mo–Co₉S₈-2 electrodes couple display superior water splitting performance with the requirement of a cell voltage of 1.50 V to drive a catalytic current density of 10 mA cm⁻², which is lower than that of RuO₂//Pt/C (1.52 V). The activity of the catalyst is greatly enhanced by the molybdenum ion doping and the instability of the sulfide is resolved. The experiment result shows that the relationship between the current density and pH is different in neutral and alkaline media, which is most be likely assigned to the change of O–O formation by transforming the reactants from water molecule to the hydroxy ion.     

A novel wavelet seismic denoising method using type II fuzzy

Wavelet based denoising of the observed non stationary time series earthquake loading has become an important process in seismic analysis. The process of denoising ensures a noise free seismic data, which is essential to extract features accurately (max acceleration, max velocity, max displacement, etc.). However, the efficiency of wavelet denoising is decided by the identification of a crucial factor called threshold. But, identification of optimal threshold is not a straight forward process as the signal involved is non-stationary. i.e. The information which separates the wavelet coefficients that correspond to the region of interest from the noisy wavelet coefficients is vague and fuzzy. Existing works discount this fact. In this article, we have presented an effective denoising procedure that uses fuzzy tool. The proposal uses type II fuzzy concept in setting the threshold. The need for type II fuzzy instead of fuzzy is discussed in this article. The proposed algorithm is compared with four current popular wavelet based procedures adopted in seismic denoising (normal shrink, Shannon entropy shrink, Tsallis entropy shrink and visu shrink).It was first applied on the synthetic accelerogram signal (gaussian waves with noise) to determine the efficiency in denoising. For a gaussian noise of sigma = 0.075, the proposed type II fuzzy based denoising algorithm generated 0.0537 root mean square error (RMSE) and 16.465 signal to noise ratio (SNR), visu shrink and normal shrink could be able to give 0.0682 RMSE with 14.38 SNR and 0.068 RMSE with 14.2 SNR, respectively. Also, Shannon and Tsallis generated 0.0602 RMSE with 15.47 SNR and 0.0610 RMSE with 15.35 SNR, respectively. The proposed method is then applied to real recorded time series accelerograms. It is found that the proposal has shown remarkable improvement in smoothening the highly noisy accelerograms. This aided in detecting the occurrence of ‘P’ and ‘S’ waves with lot more accuracy. Interestingly, we have opened a new research field by hybriding fuzzy with wavelet in seismic denoising.     

Experimental investigation on constitutive behavior of PVB under impact loading

During automotive related accidents, PVB plays an important role in both pedestrian and passenger protection as an interlayer of automotive windshield. In this paper, dynamic constitutive behavior of PVB material is thoroughly studied. Firstly, a set of dynamic compression impact experiments on PVB specimens using SHPB (Split Hopkinson Pressure Bar) method are conducted at strain rates from 700/s to 4500/s. Details of the constitutive response is analyzed based on the validation of experiment data. Stress-strain curve of PVB is then divided into two parts, i.e., “Compaction Stage” and “Hardening Stage”. Dislocations and entanglements among molecules are major reasons for the two-stage phenomena. Constitutive behaviors are different in low and high speed impacts, leading to three times more energy absorption ability of PVB in high speed impact scenario. Further, data fitting models based on both Mooney–Rivlin and Ogden Model are studied and then compared. Mooney–Rivlin Model is found to be more appropriate to describe PVB material. Moreover, PVB is proved to be a rate-dependent material with the failure strength intensify factor β ≈ 4. PVB material shows little viscoelasticity after comparison of the both models with and without the viscoelasticity part. Results offer critical experimental data, constitutive models and analysis of PVB material to further study of automotive crashworthiness and pedestrian/passenger protection.     

Improvement of optical properties of Nd:YAG transparent ceramics by post-annealing and post hot isostatic pressing

The Nd:YAG transparent ceramics were fabricated by vacuum sintering. The Nd:YAG samples were annealed at 1450 °C for 20 h in air and followed by hot isostatic pressing (HIP) at 1700 °C for 2 h in 200 MPa Ar and then re-annealed at 1250–1450 °C for 10 h in air. The experimental results showed that the optical properties of Nd:YAG samples varied markedly with different post treatments. After air annealing at 1450 °C for 20 h and HIP at 1700 °C for 2 h under 200 MPa of Ar and then air re-annealing at 1250 °C for 10 h, the transmittances of the samples increased from 51.2% to 77.2% (at 400 nm) and 78.4% to 83.6% (at 1064 nm), respectively. The annealing and HIP are effective post treatments to reduce oxygen vacancies and intergranular pores respectively in Nd:YAG transparent ceramics.     

A new approach for forecasting OPEC petroleum consumption based on neural network train by using flower pollination algorithm

Petroleum is the live wire of modern technology and its operations, with economic development being positively linked to petroleum consumption. Many meta-heuristic algorithms have been proposed in literature for the optimization of Neural Network (NN) to build a forecasting model. In this paper, as an alternative to previous methods, we propose a new flower pollination algorithm with remarkable balance between consistency and exploration for NN training to build a model for the forecasting of petroleum consumption by the Organization of the Petroleum Exporting Countries (OPEC). The proposed approach is compared with established meta-heuristic algorithms. The results show that the new proposed method outperforms existing algorithms by advancing OPEC petroleum consumption forecast accuracy and convergence speed. Our proposed method has the potential to be used as an important tool in forecasting OPEC petroleum consumption to be used by OPEC authorities and other global oil-related organizations. This will facilitate proper monitoring and control of OPEC petroleum consumption.     

Hydrogen promotes the selective catalytic reduction of NOx by ethanol over Ag/Al2O3

To understand the effect of H₂ on the selective catalytic reduction of NO_x with C₂H₅OH over Ag/Al₂O₃, surface intermediates were examined using in situ DRIFTS spectra, and by-products were identified using GC–MS. Results showed that H₂ addition promoted the partial oxidation of C₂H₅OH to form enolic species, and enhanced the reaction of NCO with NO + O₂ at low temperature. We propose that the enhancement of the enolic species was the main contributor in accelerating NO_x reduction under the presence of H₂ over Ag/Al₂O₃ at low temperatures.     

Electrospun phase change fibers based on polyethylene glycol/cellulose acetate blends

Ultrafine phase change fibers based on polyethylene glycol (PEG)/cellulose acetate (CA) blends in which PEG acts as a model phase change material (PCM) and CA acts as a supporting material, were successfully prepared via electrospinning. The effect of PEG content on the morphology, crystalline properties, phase change behaviors and tensile properties of the composite fibers was studied systematically by field-emission scanning electron microscopy (FE-SEM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and a tensile tester, respectively. The SEM observation indicates that maximum PEG content in the fibers could reach up to 70 wt%, and the morphology and average diameter of the composite fibers vary with PEG content. Thermal analysis results show that the latent heats of the phase change fibers increase with the increasing of PEG content in the fibers, and the PEG/CA fibers with high enthalpies have a good capability to regulate their interior temperature as the ambient temperature alters. Therefore, the developed phase change fibers have enormous applicable potentials in thermal energy storage and temperature regulation.     

Performance comparison of an irreversible closed Brayton cycle under maximum power density and maximum power conditions

In this paper, the power density, defined as the ratio of power output to the maximum specific volume in the cycle, is taken as objective for performance analysis of an irreversible closed Brayton cycle coupled to constant-temperature heat reservoirs in the viewpoint of finite time thermodynamics (FTT) or entropy generation minimization (EGM). The analytical formulas about the relations between power density and pressure ratio are derived with the heat resistance losses in the hot- and cold-side heat exchangers and the irreversible compression and expansion losses in the compressor and turbine. The obtained results are compared with those results obtained by using the maximum power criterion. The influences of some design parameters on the maximum power density are provided by numerical examples, and the advantages and disadvantages of maximum power density design are analyzed. The power plant design with maximum power density leads to a higher efficiency and smaller size. However, the maximum power density design requires a higher pressure ratio than maximum power design. When the heat transfer is carried out ideally, the results of this paper become those obtained in recent literature.