A Reliable Treatment for Nonlinear Differential Equations

In this paper, we use the concept of homotopy, Laplace transform, and He’s polynomials, to propose the auxiliary Laplace homotopy parameter method (ALHPM). We construct a homotopy equation consisting on two auxiliary parameters for solving nonlinear differential equations, which switch nonlinear terms with He’s polynomials. The existence of two auxiliary parameters in the homotopy equation allows us to guarantee the convergence of the obtained series. Compared with numerical techniques, the method solves nonlinear problems without any discretization and is capable to reduce computational work. We use the method for different types of singular Emden–Fowler equations. The solutions, constructed in the form of a convergent series, are in excellent agreement with the existing solutions.

Performance Analysis of Gas Wells Based on the Conventional Decline Parameters and the Flow Integral Equation

The estimation of reserves and performance prediction are two vital tasks for the development of gas reservoirs where the evaluation of gas in place or well-controlled reserves, as the foundation of the performance analysis of gas wells, turns to be exceedingly significant. Advanced production data analysis or modern rate transient analysis (RTA) methods mainly depend on the iterative calculations of material balance quasitime ( t ca ) and type curve fitting, the essence of which is to update the average reservoir pressure data time and again. The traditional Arps’ decline models are of empirical nature despite the convenience and applicability to the constant bottomhole pressure (BHP) condition. In order to avoid the implicit iteration, this paper develops an explicit method for estimating the average reservoir pressure on the basis of dynamic material balance equation (DMBE), termed “flow integral method,” which can be applied to various gas production systems under boundary-dominated flow (BDF). Based on the flow integral method and the decline parameter evaluation, we employ the hyperbolic decline model to model the gas well performance at a constant BHP. The analytical formulations of decline rate and decline exponent are deduced from the DMBE and the static material balance equation (SMBE) considering the elastic compressibilities of rock pore and bound water. The resulting decline parameter method for explicit estimation of gas reserves boasts a solid and rigorous theory foundation that production rate, decline rate, and average reservoir pressure profiles have reference to each other, and its implementation steps are explained in the paper. The SMBE can, combined with the estimated pressure profile by the flow integral method, also be used to determine gas reserves which is not limited to the constant-BHP condition and can calibrate the estimates of the decline parameter method. The proposed methods are proven effective and reliable with several numerical cases at different BHPs and a field example.

Comparison between double slope solar still and fourfold slope solar still: energy, exergy, exergoeconomic, and enviroeconomic evaluation

This paper proposes a single basin fourfold slope solar still, which includes a fourfold slope glass cover plate used for solar heat collection and steam condensation. In order to show the efficiency of fourfold slope solar still, comparative experiments are conducted under the winter climate conditions in Hangzhou for testing the operational performance of double slope type solar still (DOSS) and fourfold slope still (FOSS), so as to make a comparative analysis between them. Results show that the productivity of fourfold slope still is 19.51% higher than that of double slope still, and fourfold slope solar still enhances the average hourly energy efficiency by 31.11%. According to the energy method, the energy payback time values of fourfold slope solar still and double slope solar still are 64.88 months and 75.42 months respectively. According to the environmental parameter method, FOSS and DOSS reduce 5.47 tons and 4.58 tons of CO2 respectively. The corresponding values based on the exergy environment parameters are 0.21 and 0.18 tons of CO2, respectively. The fourfold slope solar still has more obvious emission reduction function than the double slope solar still. The cost of distilled water of fourfold slope solar still is 0.28 RMB/kg, and the cost of double slope solar still is 0.30 RMB/kg. In addition, the environmental and economic parameters of fourfold slope still and double slope still are 79.29$ (561.37RMB) and 66.35$ (469.76RMB), respectively. While, the corresponding values based on the exergoenvironmental parameter are 3.05$ (21.59RMB) and 2.56$ (18.12RMB), respectively. From the analysis of exergoeconomic and exergoenvironmental parameters, fourfold slope single basin solar still appears to be more effective.

A Super Wideband Directional Compact Vivaldi Antenna for Lower 5G and Satellite Applications

In this paper, a super wide band (SWB) Vivaldi antenna has been proposed for lower 5G bands in Sub-6 GHz and satellite applications (S, C, X, Ku, and K band) using various performance improvement techniques. In the presented Vivaldi antenna, different slots are applied not only to increase the gain and directivity but also to get operating frequency at the intended specific frequency range. All dimensions of those slots were chosen by using the sweep parameter method. Ten corrugated side slots, two circular slots, and one via have been used to enhance the performance especially bandwidth and gain of the antenna. At the edge of wireless communication, we want to enhance two key aspects within the communication systems: the quality of service and the cost. The proposed antenna incorporates a simple structure and small size with dimensions of 45 × 35 × 0.79 mm3. Thus, after design, optimization, and simulation, the antenna produces a good reflection coefficient over the very large operating bandwidth of 23.19 GHz, 1 < VSWR < 2, maximum gain of 10.2 dBi, and average radiation efficiency of above 90%, which can be recommended as a suitable antenna for lower 5G as well as satellite applications. The antenna is designed, simulated, and analyzed by using computer simulation technology microwave studio (CST-MWS). Finally, the performance of the Vivaldi antenna has been validated by FEKO and HFSS software, and we achieved a very good matching among the results.

An Equivalent Homogenization Theoretical Method for Composite Sandwich Cylinders Subjected to Pure Bending

An equivalent theoretical homogenization method was proposed for composite sandwich cylinders subjected to pure bending. Firstly, based on a homogeneous orthotropic layer hypothesis, the trapezoidal corrugated sandwich core was found to be equivalent in a homogenization orthotropic layer with the nine equivalent mechanical properties. Then, Lekhnitskii’s theory, based on a unified connection parameter method, was introduced and applied in the equivalent composite sandwich cylinder. The method developed by Lekhnitskii is suitable for arbitrary combinations of winding layers with different winding angles and materials. Additionally, the bending stiffness of the equivalent sandwich cylinder could be calculated. By developing user subroutine of UMAT, the numerical calculation results were in a good agreement with the results of the proposed method. Further, according to the Hill–Tsai strength criterion and the maximum strain criterion, parametric study was done for specified bending stiffness and specified bending strength. The results show that the influence of core parameters on the specified bending stiffness and strength are lower than that of the skin parameters. Additionally, larger skin thickness and smaller winding angles could improve the specified bending stiffness and specified bending strength of the composite corrugated sandwich cylinders.

Accurate Localization of Oil Tanks in Remote Sensing Images via FGMRST-Based CNN

Object localization is an important application of remote sensing images and the basis of information extraction. The acquired accuracy is the key factor to improve the accuracy of object structure information inversion. The floating roof oil tank is a typical cylindrical artificial object, and its top cover fluctuates up and down with the change in oil storage. Taking the oil tank as an example, this study explores the localization by combining the traditional feature parameter method and convolutional neural networks (CNNs). In this study, an improved fast radial symmetry transform (FRST) algorithm called fast gradient modulus radial symmetry transform (FGMRST) is proposed and an approach based on FGMRST combined with CNN is proposed. It effectively adds the priori of circle features to the calculation process. Compared with only using CNN, it achieves higher precision localization with fewer network layers. The experimental results based on SkySat data show that the method can effectively improve the calculation accuracy and efficiency of the same order of magnitude network, and by increasing the network depth, the accuracy still has a significant improvement.

Research on the Novel Hardware Configuration Methods of the Contact R-test Based on the Constraint Models

R-test is widely used to measure the rotary axis error of five-axis machine tools due to its high accuracy and convenient. There are some deficiencies in the research on measurement performance optimization such as the customized design under certain requirements. The novel hardware configuration methods of the contact R-test are proposed in this paper to realize customization. Firstly, the theoretical measurement model and the calibration model are established to be used as the measurement accuracy evaluation model. Secondly, the influence of hardware parameters on the measurement performance indexes of the measurement system is analyzed and the corresponding constraint models for measurement performance are established. Thirdly, the optimal configuration methods of hardware parameters based on constraint models are proposed using exhaustive search method and variable parameter method respectively . Finally, a prototype that is configured with the hardware parameters based on the above configuration methods, is developed to calibrate on the Coordinate Measuring Machine(CMM) and complete the measurement performance evaluation. The evaluation results show that the hardware configuration methods meet the certain measurement requirements without range and precision waste. The proposed methods provide guidance and reference for the customized design of contact R-test.

A novel aerial manipulator system compensation control based on ADRC and backstepping

This paper proposes a fully-actuated control method for a novel aerial manipulation system (AMS). A customized carbon frame structure supports the servo actuators, on which eight propellers group into pairs located. We present kinematics and dynamics modeling of the AMS based on Craig parameter method and recursive Newton–Euler equation, respectively. Then, an Active disturbance rejection control (ADRC)—Backstepping—Compensation controller is designed to control the exact position and orientation of the manipulator in the Cartesian space. Finally, the performance of the system is demonstrated through simulations and virtual experiments.

Investigation on the Self-synchronization of Dual Steady States for a Vibrating System with Four Unbalanced Rotors

In the field of vibration utilization engineering, to achieve the maximum degree or the highest efficiency use of the excitation force is still a hotspot among researchers. Based on this, this paper has carried out a series of synchronous theoretical analysis on the four identical unbalanced rotors (IURs) symmetrically and circularly mounted on a rigid frame (RF) model, which is used to drive a cone crusher. The dimensionless coupling equations of the four IURs are established using the improved small parameter method. The analysis of the coupling dynamics characteristics of the system shows that the four motors of the system adjust the speed through the synchronous torque to achieve synchronization, and a parameter determination method for realizing offset self-synchronization to eccentric force was put forward under the steady state of ultra-resonance. Furthermore, the relationship between the equivalent stiffness of the crushed material and crushing force and compression coefficient is discussed, and the design method of the full-load crusher working under the steady state of sub-resonance is proposed. Finally, through a series of computer simulations, the correctness of the self-synchronization of dual steady states is verified.