Direct solution of Navier-Stokes equations by using an upwind local RBF-DQ method

The differential quadrature (DQ) method is able to obtain quite accurate numerical solutions of differential equations with few grid points and less computational effort. However, the traditional DQ method is convenient only for regular regions and lacks upwind mechanism to characterize the convection of the fluid flow. In this paper, an upwind local radial basis function-based DQ (RBF-DQ) method is applied to solve the Navier-Stokes equations, instead of using an iterative algorithm for the primitive variables. The non-linear collocated equations are solved using the Levenberg-Marquardt method. The irregular regions of 2D channel flow with different obstructions situations are considered. Finally, the approach is validated by comparing the results with those obtained using the well-validated Fluent commercial package

Experimental investigation of rotordynamic coefficients for the labyrinth seals with and without shunt injection

Shunt injection serves an important role in the labyrinth seal static and rotordynamic characteristics which are important in the prediction of turbomachinery stability. This paper analyzed how the shunt injection affects the seal rotordynamic characteristics, and presented an improved impedance method based on unbalanced synchronous excitation to identify the rotordynamic coefficients of labyrinth seals on a rotor test rig. The influences of the rotational speed and the inlet/outlet pressure ratio on the rotordynamic characteristics of shunt injection seals with and without shunt injection were identified and analyzed. The experimental results reveal that all the seal rotordynamic coefficients increase with the rotational speed, and the inlet/outlet pressure ratio. The shunt injection contributes to decreasing the seal cross-coupled stiffness, and increasing the direct damping. The shunt injection plays an important role in decreasing the effective stiffness coefficient, and increasing the effective damping coefficient. The shunt injection can effectively improve the rotor stability. The experimental results lay the foundation for designing the annular seals with shunt injection

Research on probability product differentiation based on power equilibrium

Overall the benefit of Supply Chain Based on probabilistic production and power equilibrium, the influencing factors of the decision-making of probabilistic productions are studied in this paper. Firstly, the correlation function of profit is formed by solving the lowest utility of products. Then numerical simulation and example research are carried out. The results show that, there is a positive correlation property between the two types of products which formed probabilistic production and supply chain efficiency. At the same time, manufacture and retailer should also pay attention to the proportion of the two types of products in order to achieve the best overall benefit. The conclusion in this paper has practical significance, it has a significant impact on the decision-making under the power equilibrium

Market opportunity analysis of fashion blog-shops in Singapore.

A new phenomenon in the form of blog shopping is becoming increasingly prevalent amongst Singapore consumers in recent years. Blog shopping refers to the act of visiting online shops which originated from blogging platforms. This study seeks to investigate the phenomenon of blog shopping in Singapore, and also to identify market opportunities for blog-shop owners. In this study, we investigated the different expectations of female blog-shoppers from different age groups, in terms of differing preferences for payment modes, style of apparel, responses towards blogs. We also investigated the reasons why females do not blog shop. In addition, the expectations of blog-shop owners were investigated to identify any potential gaps between expectations of blog-shoppers and blog-shop owners. Finally, after identifying potential gaps or interesting trends, recommendations are provided to blog-shop owners on ways to improve their mode of operations to better meet the needs of blog-shoppers so as to capture a larger market share.BUSINES

Analysis of the Effect of Sampling Probe Geometry on Measurement Accuracy in Supersonic Gas Flow

The accuracy of sampling of gas components has a significant impact on the measurement of various performance parameters in the combustion chamber of an aero-engine. In order to investigate the effect of the probe geometry of a six-point gas sampling probe on sampling accuracy in supersonic gas flow, a three-dimensional probe gas flow characteristic solution model is established through numerical simulation methods of components of transport and fluid–solid coupling. Probes with three angles of 28°, 30°, and 32° and an optimized conical probe are constructed. The sampling accuracy of the probes with different geometries is compared and evaluated by the deviation of the component volume fraction before and after sampling and the resulting combustion efficiency error. This paper presents a set of calculation methods for solving the relative deviation of volume fraction by an iterative method based on the ideal gas law and the Redlich–Kwong equation (R-K equation). The method is designed to solve the exact component volume fraction problem in the simulation calculation. The study results demonstrate that the 28° and optimized conical probes improve sampling accuracy more effectively than the original 30° structure. The deviation of the volume fractions of the two structures is less than 1.7%, and the combustion efficiency error is less than 0.09%. The developed iterative calculation method can significantly reduce the theoretical calculation error to less than 0.06%. The experimental data of the test bench are in good agreement with the simulation results, thereby demonstrating the reliability and accuracy of the sampling probe following structural optimization

Fault Diagnosis of Intershaft Bearings Using Fusion Information Exergy Distance Method

For the fault diagnosis of intershaft bearings, the fusion information exergy distance method (FIEDM) is proposed by fusing four information exergies, such as singular spectrum exergy, power spectrum exergy, wavelet energy spectrum exergy, and wavelet space spectrum exergy, which are extracted from acoustic emission (AE) signals under multiple rotational speeds and multimeasuring points. The theory of FIEDM is investigated based on four information exergy distances under multirotational speeds. As for rolling bearings, four faults and one normal condition are simulated on a birotor test rig to collect the AE signals, in which the four faults are inner ring fault, outer ring fault, rolling element fault, and inner race-rolling element coupling fault. The faults of the intershaft bearings are analyzed and diagnosed by using the FIEDM. From the investigation, it is demonstrated that the faults of the intershaft bearings are accurately diagnosed and identified, and the FIEDM is effective for the analysis and diagnosis of intershaft bearing faults. Furthermore, the fault diagnosis precision of intershaft bearings becomes higher with increasing rotational speed

Multi-Domain Entropy-Random Forest Method for the Fusion Diagnosis of Inter-Shaft Bearing Faults with Acoustic Emission Signals

Inter-shaft bearing as a key component of turbomachinery is a major source of catastrophic accidents. Due to the requirement of high sampling frequency and high sensitivity to impact signals, AE (Acoustic Emission) signals are widely applied to monitor and diagnose inter-shaft bearing faults. With respect to the nonstationary and nonlinear of inter-shaft bearing AE signals, this paper presents a novel fault diagnosis method of inter-shaft bearing called the multi-domain entropy-random forest (MDERF) method by fusing multi-domain entropy and random forest. Firstly, the simulation test of inter-shaft bearing faults is conducted to simulate the typical fault modes of inter-shaft bearing and collect the data of AE signals. Secondly, multi-domain entropy is proposed as a feature extraction approach to extract the four entropies of AE signal. Finally, the samples in the built set are divided into two subsets to train and establish the random forest model of bearing fault diagnosis, respectively. The effectiveness and generalization ability of the developed model are verified based on the other experimental data. The proposed fault diagnosis method is validated to hold good generalization ability and high diagnostic accuracy (~0.9375) without over-fitting phenomenon in the fault diagnosis of bearing shaft

The Effects of Plastic Mulching Combined with Different Fertilizer Applications on Greenhouse Gas Emissions and Intensity, and Apple Yield in Northwestern China

Plastic mulching reduces weeds, conserves soil water, and boosts crop yield. However, most studies are insufficient when determining how plastic mulching affects greenhouse gas (GHG) emissions, particularly when used in conjunction with fertilizers. The purpose of this study was to determine the combined effect of plastic mulching and fertilizers on GHG emissions in apple orchards. A 3-year field experiment was conducted with two factors: mulching and fertilizers; (1) mulching treatments: plastic film (PM) and no mulching (NM); and (2) four fertilizer treatments: control (CK), organic fertilizer (M), inorganic fertilizer (NPK), and organic combined with inorganic fertilizer (MNPK), arranged in a two factorial randomized complete block design. The results showed that the mean annual N2O emissions ranged from 0.87 to 5.07 kg ha−1 in PM and from 0.75 to 2.90 kg ha−1 in NM. The mean CO2 emissions ranged from 2.10 to 6.68 t ha−1 in PM and from 1.98 to 4.27 t ha−1 in NM. MNPK contributed more to N2O and CO2 emissions in both PM and NM. The mean CH4 uptake rate ranged from 1.19 to 4.25 kg ha−1 in PM and from 1.14 to 6.75 kg ha−1 in NM. M treatment contributed more to CH4 uptake in both PM and NM. NKP treatments had higher greenhouse gas intensity (GHGI) in PM and NM, while MNPK and NPK treatments had higher greenhouse gas potential (GWP) in PM and NM, respectively. These results suggest that plastic film mulching significantly raises the potential for soil GHG emissions and increases apple yield

Diverse Banana Pseudostems and Rachis Are Distinctive for Edible Carbohydrates and Lignocellulose Saccharification towards High Bioethanol Production under Chemical and Liquid Hot Water Pretreatments

Banana is a major fruit crop throughout the world with abundant lignocellulose in the pseudostem and rachis residues for biofuel production. In this study, we collected a total of 11 pseudostems and rachis samples that were originally derived from different genetic types and ecological locations of banana crops and then examined largely varied edible carbohydrates (soluble sugars, starch) and lignocellulose compositions. By performing chemical (H2SO4, NaOH) and liquid hot water (LHW) pretreatments, we also found a remarkable variation in biomass enzymatic saccharification and bioethanol production among all banana samples examined. Consequently, this study identified a desirable banana (Refen1, subgroup Pisang Awak) crop containing large amounts of edible carbohydrates and completely digestible lignocellulose, which could be combined to achieve the highest bioethanol yields of 31–38% (% dry matter), compared with previously reported ones in other bioenergy crops. Chemical analysis further indicated that the cellulose CrI and lignin G-monomer should be two major recalcitrant factors affecting biomass enzymatic saccharification in banana pseudostems and rachis. Therefore, this study not only examined rich edible carbohydrates for food in the banana pseudostems but also detected digestible lignocellulose for bioethanol production in rachis tissue, providing a strategy applicable for genetic breeding and biomass processing in banana crops

Superconducting Behavior of BaTi₂(Sb_1–<i>y</i>Bi_<i>y</i>)₂O under Pressure

The crystal structure and superconducting properties of a new type of titanium–pnictide superconductor, BaTi2(Sb1–yBiy)2O (y = 0.2, 0.5, and 0.8), are comprehensively investigated over a wide pressure range to elucidate the effect of substituting Bi for Sb on the superconducting behavior. The behavior of superconducting properties under pressure changes drastically with y, as expected from the double-dome Tc–y phase diagram obtained at ambient pressure. In this study, three BaTi2(Sb1–yBiy)2O samples (y = 0.2, 0.5, and 0.8) are considered, which correspond to the first superconducting dome, nonsuperconducting part, and second superconducting dome, respectively, in the Tc–y phase diagram. The crystal of BaTi2(Sb1–yBiy)2O with y = 0.2 shows a clear collapse transition, i.e., a drastic shrinkage of the lattice constant c at ca. 5 GPa. Strictly speaking, the collapsed crystal phase coexists with the noncollapsed phase above 5 GPa. On the other hand, BaTi2(Sb1–yBiy)2O with y = 0.8 shows a continuous change in the crystal lattice with pressure, i.e., no collapse transitions. The pressure dependence of Tc for BaTi2(Sb1–yBiy)2O with y = 0.2 shows a drastic increase in Tc at approximately 5 GPa, where the collapse transition occurs, indicating a clear pressure-induced superconducting phase transition related to the collapse transition. The value of Tc for BaTi2(Sb1–yBiy)2O with y = 0.8 increases slightly up to ∼2 GPa and is almost constant at 2–13 GPa. It is found that the superconducting behavior under pressure can be unambiguously classified by y based on the double-dome Tc–y phase diagram, indicative of distinguishable superconducting features at different y values. In this study, we comprehensively discuss the superconducting properties of the exotic material, BaTi2(Sb1–yBiy)2O, with a double-dome Tc–y phase diagram