Flexible supporting and fixing method for hybrid ultrasonic motor using longitudinal and torsional vibration modes

A new flexible supporting and fixing method for hybrid ultrasonic motor using longitudinal and torsional vibration modes is presented. A motor base is used to support and fix the motor, which has dual concentric bearings in opposite shell sides and a fixing slot. The axis of the motor has two extended parts outside the both sides of the motor. Once the motor has been assembled completely, the two extended parts of the motor axis will be inserted into the concentric bearings, which support the motor and restrict several degrees of freedom (DOFs) of the motor, such as the translational DOFs along X and Y axes, the rotational DOFs around X and Y axes. The motor has a flexible fixing sheet which placed near the piezoelectric ceramics, and the flexibility of the fixing is discussed by analyzing the thickness and the foot length of fixing sheet. The fixing sheet is fixed on the fixing slot with glue, which restricts the translational DOF along Z axis and rotational DOF around Z axis of the stator. The experiment results show that there is little influence on the motor working performance by using this supporting and fixing method; the motor can work smoothly and steadily and the maximum speed of the motor can exceed 2000 r/min

A bio-inspired flapping wing rotor of variant frequency driven by ultrasonic motor

By combining the flapping and rotary motion, a bio-inspired flapping wing rotor (FWR) is a unique kinematics of motion. It can produce a significantly greater aerodynamic lift and efficiency than mimicking the insect wings in a vertical take-off and landing (VTOL). To produce the same lift, the FWR’s flapping frequency, twist angle, and self-propelling rotational speed is significantly smaller than the insect-like flapping wings and rotors. Like its opponents, however, the effect of variant flapping frequency (VFF) of a FWR, during a flapping cycle on its aerodynamic characteristics and efficiency, remains to be evaluated. A FWR model is built to carry out experimental work. To be able to vary the flapping frequency rapidly during a stroke, an ultrasonic motor (USM) is used to drive the FWR. Experiment and numerical simulation using computational fluid dynamics (CFD) are performed in a VFF range versus the usual constant flapping frequency (CFF) cases. The measured lifting forces agree very well with the CFD results. Flapping frequency in an up-stroke is smaller than a down-stroke, and the negative lift and inertia forces can be reduced significantly. The average lift of the FWR where the motion in VFF is greater than the CFF, in the same input motor power or equivalent flapping frequency. In other words, the required power for a VFF case to produce a specified lift is less than a CFF case. For this FWR model, the optimal installation angle of the wings for high lift and efficiency is found to be 30° and the Strouhal number of the VFF cases is between 0.3–0.36. View Full-Tex

An exact solution for the magnetic diffusion problem with a step-function resistivity model

In the magnetic diffusion problem, a magnetic diffusion equation is coupled by an Ohmic heating energy equation. The Ohmic heating can make the magnetic diffusion coefficient (i. e., the resistivity) vary violently, and make the diffusion a highly nonlinear process. For this reason, the problem is normally very hard to be solved analytically. In this article, under the condition of a step-function resistivity and a constant boundary magnetic field, we successfully derived an exact solution for this nonlinear problem, which should be an interesting thing in the area of partial differential equations. What's more, the solution could serve as a valuable benchmark example for testing simulation methods of the magnetic diffusion problem.Comment: 10 pages, 5 figure

Risk Analysis for the Urban Buried Gas Pipeline With Fuzzy Comprehensive Assessment Method 1

Based on the statistical analysis from a great deal of failure cases, generally, the failure causes of buried pipeline can be classified into four factors, namely, third-party damage, erosion-corrosion damage, design and construction error, and incorrect operation. The factors influencing the failure of pipeline are complicated, varied and fuzzy. Especially, the influence factors of third-party damage of buried pipeline are of the character of fuzziness, which are difficult to express with the accurate mathematic models. In this paper, the failure factors of buried gas pipeline are first analyzed by fault tree analysis method. Then, the failure likelihood and failure consequence, two parts of the risk, are evaluated with fuzzy comprehensive assessment method, respectively. Finally, the in-service risk of the buried gas pipeline for a certain city is expressed by the risk matrix, which is established with the failure likelihood as vertical ordinate and the failure consequence as horizontal ordinate. It is concluded that there are two pipeline units belong to high risk category, 24 pipeline units belong to medium-high risk category, 160 pipeline units belong to medium risk category, and 392 pipeline units belong to low risk category

Improving recovery efficiency by CO2 injection at late stage of steam assisted gravity drainage

The high recovery performance of steam-assisted gravity drainage (SAGD) makes it a popular option for heavy oil resources. Currently, most of the heavy oil reservoirs developed by SAGD in China are in the late development phase, with high energy consumption due to reduced thermal efficiency. The use of SAGD wind-down processes involving CO2 in combination with steam for heavy oil recovery is considered as a viable alternative to limit energy consumption, and also reduce the amount of greenhouse gas emissions by leaving CO2 behind in the reservoir. Study reveals that the dissolution and demulsification of CO2 steam chamber temperature reaches 200 ◦C, the amount of solid phase deposition induced in crude oil can reduce the viscosity of emulsified heavy oil by more than 50%. When the by CO2 extraction is only 0.016 kg/m3 , the rock wettability changes from lipophilic to hydrophilic, and the higher the reservoir temperature, the stronger the hydrophilicity is, which reduces the adhesion power of the oil phase and facilitates the stripping of crude oil from the rock surface. Numerical simulation studies have been carried out utilizing STARS to obtain energy efficient utilization and improved steam chamber characteristics. Heat loss from SAGD baseline is 1.77 times that with CO2 injection process, but the recovery factor is only 2.48% higher. At the initial stage with CO2 injection, the steam chamber continues its lateral expanding, which increases the recovery factor at the initial stage of CO2 injection by about 6%. One year after CO2 injection, gas channeling results in lower recovery than traditional SAGD process, and 38.4% of the injected CO2 is stored in the reservoir from this study.Cited as: Gong, H., Yu, C., Jiang, Q., Su, N., Zhao, X., Fan, Z. Improving recovery efficiency by CO2 injection at late stage of steam assisted gravity drainage. Advances in Geo-Energy Research, 2022, 6(4): 276-285. https://doi.org/10.46690/ager.2022.04.0

First detection of small hive beetle Aethina tumida Murray (Coleoptera: Nitidulidae) infesting eastern honeybee, Apis cerana Fabricius (Hymenoptera: Apidae), in China

We report the infestation of small hive beetle, Aethina tumida, in a honeybee, Apis cerana, in South China. This is the first record for domestic Chinese honey bee infested with small hive beetle

Comprehensive evaluation research of hybrid energy systems driven by renewable energy based on fuzzy multi-criteria decision-making

The worsening of climate conditions is closely related to the large amount of carbon dioxide produced by human use of fossil fuels. Under the guidance of the goal of “carbon peaking and carbon neutrality goals”, with the deepening of the structural reform of the energy supply side, the hybrid energy system coupled with renewable energy has become an important means to solve the energy problem. This paper focuses on the comprehensive evaluation of hybrid energy systems. A complete decision support system is constructed in this study. The system primarily consists of four components: 1) Twelve evaluation criteria from economic, environmental, technological, and socio-political perspectives; 2) A decision information collecting and processing method in uncertain environment combining triangular fuzzy numbers and hesitation fuzzy language term sets; 3) A comprehensive weighting method based on Lagrange optimization theory; 4) Solution ranking based on the fuzzy VIKOR method that considers the risk preferences of decision-makers. Through a case study, it was found that the four most important criteria are investment cost, comprehensive energy efficiency, dynamic payback period and energy supply reliability with weights of 7.21%, 7.17%, 7.17%, and 7.15% respectively. A1 is the scheme with the best comprehensive benefit. The selection of solutions may vary depending on the decision-maker’s risk preference. Through the aforementioned research, the decision framework enables the evaluation of the overall performance of the system and provides decision-making references for decision-makers in selecting solutions