Zhengying Wei

Effect of large-area texture/slip surface on journal bearing considering cavitation

Purpose – The purpose of this paper is to study the influence of large-area texture/slip surface, especially the area and position of large-area texture surface on journal bearing, and improve the tribological performances of journal bearing. Design/methodology/approach – A modified texture/slip numerical boundary condition with double parameters is presented and is applied onto the region where surface textures locate to represent the impact of actual texture/slip surface. A phase change condition is used to analyze cavitation phenomena. Findings – The global/cumulative texture effect can be represented by applying texture/slip condition onto the region where it locates. The area and position of texture/slip surface would significantly affect the cavitation and load-carrying capacity. Texture/slip surface would not affect the pressure and load-carrying capacity when it locates at cavitation zone. The effect of texture/slip surface on load-carrying capacity would be beneficial if it locates at the pressur...

Rapid development technique for drip irrigation emitters

This paper describes the rapid development process for emitter which is the key part in water‐saving irrigation device. The design of labyrinth‐channel in emitters, the generation of process‐oriented structural CAD model, the building of emitter prototype and its integrative experimental model based on RP are introduced in detail. The emitter prototypes can be directly applied to irrigation experiments and production practice, and hence the rapid development of drip irrigation emitters can be realized.

Rapid structural design of drip irrigation emitters based on RP technology

Purpose – The paper aims to summarize the design theory for labyrinth channels of water saving emitters.Design/methodology/approach – On the basis of extracting the structural parameters of labyrinth channels in water saving emitters, the hydraulic performance experiments on the integral emitters fabricated with higher resolution rapid prototyping technology are performed. Then, using multivariable linear regression, formulas of pressure versus flow rate and regression plots for different emitters are induced.Findings – The formulas of flow rate versus structural parameters are summarized based on the trapezoid‐type channel unit, and verified through experiments. The relationships between flow rate, pressure and structural parameters of channels are established.Research limitations/implications – The effect of emitter fabrication error on the flow rate is analyzed, which provides a basis for parameterized structural design and accuracy control in the fabrication of future emitters.Practical implications –...

Effects of the slip surface on the tribological performances of high-speed hybrid journal bearings

The slip surface has a significant effect on the tribological performances of a slider bearing and a hydrodynamic journal bearing. Less attention has been paid to the influence of a boundary slip on a hybrid journal bearing. However, hybrid journal bearings are increasingly used due to their intrinsic advantages. The effects of slip surface on the performances of a hybrid journal bearing are studied in this work. The affecting rule of both the slip-region location and the size on the load-carrying capacity is obtained. Only a well-designed slip surface could improve the tribological performances of hybrid journal bearings. This work could provide a valuable guide for the design of a slip surface in high-speed hybrid journal bearings.

Effect of recess configuration on the performances of high-speed hybrid journal bearing

Purpose The purpose of this paper is to study the influences of recess configurations on the performances of high-speed hybrid journal bearing. Hybrid journal bearing earns increasing attention in high-speed machine tool spindle owing to its intrinsic outstanding performances of low temperature rise and high stability. Design/methodology/approach To investigate the coupled effects of temperature, turbulence and the interaction between lubricant and journal/bearing bush, a thermal fluid-structure interaction approach is presented and validated by the experimental results. Findings Ladder-type recess has excellent tribological characteristics in decreasing temperature rise, improving stability and inhibiting cavitation, which are all beneficial to improve the performances of high-speed spindle system. Originality/value This work can be a valuable guide for the future high-speed hybrid journal bearing design.

RESEARCH ON TRANSITIONAL FLOW CHARACTERISTICS OF LABYRINTHCHANNEL EMITTER

A physical model for flow characteristics analysis of labyrinth-channel emitter is reconstructed by Reverse Engineering from an injection molded part, and both laminar flow and turbulence models are adopted to simulate the flow state under the condition of low Reynolds numbers. According to the distribution of separation and reattachment points, the onset of transition from laminar to turbulent flow in labyrinth channels occurs at a range of Re=250~300. Furthermore, a visualization system of the flow field inside the labyrinth experiments. The experiment of tracing particles verifies the calculated flow field distribution, and another experiment using dyeing liquor showed the critical Reynolds number characterizing the transition, which is reasonably consistent with numerical simulation results. The critical Reynolds number obtained shows the fact that the flow inside this emitter is turbulent under the pressures of 40~150 kPa.

Numerical analysis of impact of imprinting pressure on profile shape and mold deformation in UV-NIL

In this paper, in order to reveal the interrelationship among the imprinting pressure, the evolution profile and the mold deformation, a novel numerical model accounted for surface tension and contact angle was established to simulate the resist filling process and mold deformation by using computational fluid dynamics(CFD). As a basic study to understand the resist filling characteristics in UV-NIL, we had chosen a simple rectangular cavity as a computational domain. In order to fully account for the effect of imprinting pressure, numerical simulations have been performed for different imprinting pressure. The evolution profile of the resist and mold deformation was found to be significantly influenced by the imprinting pressure. Numerical results show that a higher imprinting pressure will make the profile shape of resist more flat, which can improve the filling rate of the resist and reduce the filling time. However, too high imprinting pressure is easy to cause larger mold deformation that is unfavorable to the demoulding process and finial quality of imprinted pattern. Through a synthetic consideration of the influence of the imprinting pressure on the evolution profile and the mold deformation, we considered that the optimum imprinting pressure should be about 0.1MPa.

Detection of eggshell crack using electronic nose.

The objective of this study was to investigate the potential of an electronic nose (E-nose) technique for detecting eggshell crack. An E-nose was developed with eight sensors for distinguishing intact eggs and cracked eggs. Pattern recognition was conducted using principal component analysis (PCA), linear discriminant analysis (LDA), back-propagation neural network (BPNN), and the combination of genetic algorithm and BP neural network (GANN). The results proved that the E-nose coupled with LDA and PCA can distinguish between intact egg and cracked egg after one week or two weeks of storage, and the LDA method had better classification results. Furthermore, the E-nose using BPNN and GANN can distinguish between intact egg and cracked egg, and a greater distinguishing effect can be obtained with increased storage time. A better predicted rate was obtained by GANN than by BPNN.

Improved online sequential extreme learning machine for simulation of daily reference evapotranspiration

Yubin, Z., Zhengying, W., Lei, Z., Qinyin, L., & Jun, D. (March-April, 2017). Improved online sequential extreme learning machine for simulation of daily reference evapotranspiration. Water Technology and Sciences (in Spanish), 8(2), 127-140. The traditional extreme learning machine has significant disadvantages, including slow training, difficulty in selecting parameters, and difficulty in setting the singularity and the data sample. A prediction model of an improved Online Sequential Extreme Learning Machine (IOS-ELM) of daily reference crop evapotranspiration is therefore examined in this paper. The different manipulation of the inverse of the matrix is made according to the optimal solution and using a regularization factor at the same time in the model. The flexibility of the IOS-ELM in ET0 modeling was assessed using the original meteorological data (Tmax, Tm, Tmin, n, Uh, RHm, φ, Z) of the years 1971–2014 in Yulin, Ankang, Hanzhong, and Xi’an of Shaanxi, China. Those eight parameters were used as the input, while the reference evapotranspiration values were the output. In addition, the ELM, LSSVM, Hargreaves, Priestley-Taylor, Mc Cloud and IOS-ELM models were tested against the FAO- 56 PM model by the performance criteria. The experimental results demonstrate that the performance of IOS-ELM was better than the ELM and LSSVM and significantly better than the other empirical models. Furthermore, when the total ET0 estimation of the models was compared by the relative error, the results of the intelligent algorithms were better than empirical models at rates lower than 5%, but the gross ET0 empirical models mainly had 12% to 64.60% relative error. This research could provide a reference to accurate ET0 estimation by meteorological data and give accurate predictions of crop water requirements, resulting in intelligent irrigation decisions in Shaanxi.

Doping Ag in ZnO Nanorods to Improve the Performance of Related Enzymatic Glucose Sensors

In this paper, the performance of a zinc oxide (ZnO) nanorod-based enzymatic glucose sensor was enhanced with silver (Ag)-doped ZnO (ZnO-Ag) nanorods. The effect of the doped Ag on the surface morphologies, wettability, and electron transfer capability of the ZnO-Ag nanorods, as well as the catalytic character of glucose oxidase (GOx) and the performance of the glucose sensor was investigated. The results indicate that the doped Ag slightly weakens the surface roughness and hydrophilicity of the ZnO-Ag nanorods, but remarkably increases their electron transfer ability and enhances the catalytic character of GOx. Consequently, the combined effects of the above influencing factors lead to a notable improvement of the performance of the glucose sensor, that is, the sensitivity increases and the detection limit decreases. The optimal amount of the doped Ag is determined to be 2 mM, and the corresponding glucose sensor exhibits a sensitivity of 3.85 μA/(mM·cm2), detection limit of 1.5 μM, linear range of 1.5 × 10−3–6.5 mM, and Michaelis-Menten constant of 3.87 mM. Moreover, the glucose sensor shows excellent selectivity to urea, ascorbic acid, and uric acid, in addition to displaying good storage stability. These results demonstrate that ZnO-Ag nanorods are promising matrix materials for the construction of other enzymatic biosensors.