Design of X-type unmanned quadrotor based on STM32北大核心CSCD

For the flight attitude control of unmanned quadrotor, there still exist some issues on accurate measurement, calculation and output. To acquire a stable flight attitude control, an X-type unmanned quadrotor was designed based on STM32 microprocessor. Dual processors, dual gyroscopes and dual accelerometers were integrated into the hardware architecture. Real time flight attitude information was collected. Quaternion complementary filter algorithm and cascade PID control algorithm were adopted in attitude calculation and output. The experiment results showed that the structure of dual gyroscopes and dual accelerometers had higher measurement accuracy under little angle disturbance, and the attitude angle got a smaller output error with appropriate parameter settings of cascade PID. The results demonstrate that dual sensors can perform stronger noise immunity in attitude measurement, and the designed X-type unmanned quadrotor has good flying performance and can achieve the purpose of flight attitude stability control, which provides guidance for further study on flight control system.     

Research on cultural and creative product design method based on case北大核心CSCD

Aiming at the design of cultural product modeling,design elements related to product modeling were subdivided into five aspects, including function, behavior, culture, emotion and structure method. Cultural and creative product concept prototype system was built to design culture creative products by combining case-based design technology, genetic algorithm and shape grammar knowledge. The system was built to guide designers to design some cultural products. A multi-objective optimization model of design element oriented on product modeling was proposed, and the matching operations on the user demand was made. The design method model of cultural products modeling was presented, which combined with the knowledge of product gene tree crossover operation and shape grammar, and a crossing and recombinant of design elements between modern products and cultural artifacts was made. Through the in-depth study of product modeling design elements, and integrating case-based reasoning, genetic algorithm and the shape grammar knowledge into cultural and creative product concept prototype system, it was proved that the system was able to aid the designers to make some creative designs. An example of the design on small speakers was used to verify the feasibility of this method. An effective design method on cultural product design is provided.     

Study on simulation method of antenna electromechanical coupling based on model reconstruction北大核心CSCD

Electromechanical coupling involving the interaction of mechanics, electromagnetics and thermotics, which has a direct impact on product's performance. Data transfer between different physical fields is the key to the electromechanical coupling simulation. An method based on model reconstruction to analyze the electromechanical coupling of microwave antenna was presented and a simulation platform was developed. In the simulation platform, firstly, the mechanical analysis was carried out by ANSYS. Secondly, the APDL language was applied to obtain and export the deformed mesh of the structural analysis, and the deformation geometric entities was reconstructed by the Non-Uniform Rational B-Spline (NURBS) theory and deformed mesh. Finally, the deformation entities were imported into the HFSS (electromagnetic field analysis software) to calculate the performance of the deformation of antenna. The waveguide slot antenna was applied to verify the correctness between the method and measurement results. The study shows that the electromechanical coupling will affect the performance of antenna. This method can be used to analyze the electromechanical coupling of antenna at design stage.     

Research for high-precision feed system based on 3D printer of FDM北大核心CSCD

In order to improve accuracy and quality of print moldings, high-precision feed system based on 3D printer of FDM and the implement method is improved. This system used IRF530N power tube, heating pipe and PWM as a Heating Module; Pt100 platinum thermistor, differential amplifier circuit and PID Algorithm as a Temperature Measuring and Controlling Module. It not only simplified the calculation of scale changes, but also reduced the influence of the measurement of resistance drift. Based on feeding control module of the stepping motor, some measures for reducing the phenomenon of the stepper motor which losed step were given. The realization of constant temperature control of 180-250°C range, ±1°C accuracy can guarantee the constant temperature and high precision feeding of 3D printer of FDM. It can also be used to control the humidity, pressure, displacement and angle and other physical quantities.     

Simulation and experimental study on plug and pull characteristic of electrical connector contact北大核心CSCD

In order to find the changes of each monitoring measurement in the process of plug and pull of electrical connector contacts, concerning the influence of different structure parameters on plug and pull characteristic of electric connectors,the process of plug and pull was simulated by ANSYS. The changes of jack strip deformation, stress distribution, plug and pull force and contact force were surveyed, and the change law of contact force and other parameters was analysed with different structure size of the contact.The analysis showed that the variation of the shrinkage had the noticeable influence on each monitoring measurement followed by the jack strip length and thickness, and slot width had a little effect on the contact. The results showed that the finite element method could simulate the changes of the monitoring measurement in the process of plug and pull of contact preferably. The method can provide basis for the design and reliability test of electrical connector contact.     

Product low-carbon innovative design based on the carbon footprint information model北大核心CSCD

Aiming at further alleviating global warming and reducing carbon emission in product life cycle from source, low-carbon design has increasingly becoming an important direction of product design. Based on exploring the composition of decision making information and corresponding choice of design strategy in low-carbon design process, a carbon emission integrated product low-carbon design information model was established. Based on the analysis of information connotation within low-carbon design decision making, a double progressive positioning method of carbon footprint source features which was based on product structural tree and detailed design parameters was proposed, in which streamlined life cycle assessment (SLCA) using qualitative/semi-quantitative matrix approach was used to preliminarily screen the key structural units with high emission, then the key design features and parameters were stepwisely positioned by weight assigned relation digraph. With regard to design parameters related conflicts, TRIZ conflict resolution theory was used. Finally, a handled vacuum cleaner was used as an example to prove the feasibility and effectiveness of the method.     

The sensitivity of the β-material parameter and its determination based on optimization of error in the mechanical properties

The β-material is an extremely useful parameter for the analysis of nanoindentation data as it correlates different nanomechanical quantities and greatly simplifies the conventional Oliver and Pharr method used for determination of mechanical properties. Primarily, it may be determined both by fitting several sets of experimental data relating two nanomechanical quantities and from the total energy dissipated during indentation. While the first method is very cumbersome, the second may yield erroneous value for some materials. Reexamination of the experimental data on three ceramics available in the literature reveals that this parameter is very sensitive. Even a small error in its approximation may lead to a substantial error in the computation of initial unloading stiffness, contact area, elastic modulus and hardness values in certain conditions, and therefore, it must be determined very precisely. In this paper, a method for the determination of the β-material parameter based on the optimization of error in mechanical properties is proposed. β determined using the proposed technique not only ensures the goodness of fit to the experimental data but also satisfies the loop conditions more precisely.     

Super-short-time wind power combination forecasting based on support vector machine optimized by EMD-SC and AGSA北大核心CSCD

Due to the randomness, volatility and relativity of the wind power, it brings great challenges to wind power integration. To improve the ultra short-term prediction accuracy of the wind power, a kind of method for predicting super-short-term wind power based on empirical mode decomposition (EMD) and spectral clustering (SC) and ameliorated gravitational search algorithm (AGSA) that could optimize the learning parameters of support vector machine (SVM) was put forward. Firstly, the raw data of the wind power was denoised by EMD to eliminate the irregular data; then the cluster analysis of the subsequences from EMD was carried out by SC, and SVM's model was optimized by applying AGSA to predict each subsequence respectively; finally the results of the subsequences were added together to get the ultimate predicted value. Taking one wind farm's actual data as an example, the simulation indicates that the proposed model can improve the accuracy and veracity when predicting wind power. Meanwhile, it also suggests the reasonability of this method. The method can forecast wind power accurately.     

Aims and Scope of New Carbon Materials北大核心CSCD

New Carbon Materialspublishes research devoted to the physics,chemistry and technology of those organicsubstances that are precursors for producing aromatically or tetrahedrally bonded carbonaceous solids,and of thematerials that may be produced from those organic precursors.These materials range from diamond and graphitethrough chars,semicokes,mesophase substances,carbons,carbon fibers。     

The application software of the CERN PS accelerator controls system — analysis of its cost and resources

The CERN PS accelerators have evolved into one of the world's most sophisticated high energy physics facility. The variety of beams and their high repetition rate means that a most sophisticated controls system is required. This reflects on the application software. At the time of the completion of the new control system, nearly 1000 programs, amounting to around 450 000 lines of code, have been developed at the cost of approximately 120 man-years. The span of this software ranges from real-time application programs to special purpose development and management tools.This paper documents the cost, resources and production of this software project. These are analyzed in terms of the structure of the application software. Rules-of-thumb are suggested for estimating the required effort at various phases of the project and to define the implementation strategy.     

Research progress on electrode materials and electrolytes for supercapacitors北大核心CSCD

Supercapacitors have great potential applications for electronic devices, and energy recyling and storage areas owing to their high power density, long cycle life, high safety and excellent performance at low temperatures. The electrode materials and electrolytes are two key factors that influence their performance. The electrode materials used in supercapacitors include carbon materials such as activated carbons, carbon nanotubes, graphene, carbon nanofibers and carbon nano-onions, metal oxides, conductive polymers and their composites. The electrolytes are aqueous electrolytes, organic electrolytes or ionic liquids. Here research progress on the electrode materials and liquid electrolytes for supercapacitors is summarized, their advantages and disadvantages are analyzed, and new electrode materials and electrolytes are suggested.     

The hydrothermal synthesis of beta-Ni(OH)(2) nanoflakes on carbon cloth and their electrochemical properties北大核心CSCD

Carbon cloth (CC) coated with beta-Ni(OH)(2) nanoflakes was prepared by a hydrothermal method using nickel nitrate, urea and ammonium fluoride as the reaction system, and was characterized by SEM, XPS and XRD. Results indicated that the acid treatment of the CC introduced more active functional groups on its surface, which was beneficial to the coating of the beta-Ni(OH)(2). The beta-Ni(OH)(2) nanoflakes were of high purity; and their formation mechanism on the CC was investigated by observing their morphology at different reaction times. It was revealed that the beta-Ni(OH)(2) were initially present in the form of discrete nanoparticles and nanoflakes and after 6 h formed a continuous and well-crystallized beta-Ni(OH)(2) nanoflake with diameter and thickness of 1 mu m and 10 nm, respectively. Nanoflakes continued to form, grow and overlap and after 12 h the thickness had increased to 200 nm. The sample at 6 h had the highest specific capacitance of 815. 67 F.g(-1) at a current density of 1 A.g(-1) and retained 98. 1% of its initial capacitance after 4 000 cycles.     

Finite element simulation and experimental research on rotary ultrasonic grinding of titanium alloy北大核心CSCD

In order to study the effects of the abrasive grain size of core tool on grinding force in rotary ultrasonic grinding titanium alloy, abrasive grain in the shape of irregular polyhedron was modeled by cutting regular hexahedron with random interception plane on a hexahedron. Based on virtual grid method, a simulation model of core drill with multi abrasive grains randomly distributing on the end face of tool was built. A 3D finite element model of rotary ultrasonic grinding of titanium alloy was developed by using Deform-3D. The simulation value of grinding force in rotary ultrasonic grinding of titanium alloy Ti6Al4V with multi abrasive grains was obtained by Lagrangian incremental algorithm, and the effects of the abrasive grain size on grinding force was investigated. A series of experiments were conducted to validate the grinding force in rotary ultrasonic grinding of titanium alloy. The result proved that rotary ultrasonic grinding force decreased as abrasive grain size increased and the experimental result agreed well with the simulation result. The result shows that the multi abrasive grain tool model and the finite element model of rotary ultrasonic grinding have certain accuracy. A new way for multi abrasive grain tool relational investigation in rotary ultrasonic grinding has been provided.     

The effects of activation method on the pore structure and electrochemical properties of ordered mesoporous carbons used as the electrode materials of supercapacitors北大核心CSCD

An ordered mesoporous carbon. (OMC) synthesized by the soft-template method was activated by (a) CO2 at 900 degrees C for 4 h, (b) H2O at 800 degrees C for 20 min, and (c) H2O at 800 degrees C for 20 min followed by CO2 at 900 degrees C for 4 h to produce three micro-mesoporous carbons, A1, A2 and A3, respectively. Their pore structures were investigated by XRD, TEM, SEM and N-2 adsorption. Their electrochemical properties as the electrode materials of supercapacitors were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Results indicated that the highly ordered 2D hexagonal original mesostructure of the OMC was well retained after activation. The increasing order of the extent of activation is A1相似文献   

Design and analysis of turnover platform for welding robot北大核心CSCD

A turnover platform for welding robot was designed for the application of welding robot with lower accuracy requirement, which was of low cost and higher position accuracy. In this turnover platform, the pneumatic motor was used as the power output, and the indexing mechanism with high accuracy was the transmission system with high transmitting ratio based on worm and wheel. The position information was acquired by using the photoelectric encoder, and the turnover motion with high accuracy was realized through the closed-loop controller. Simulation results showed that the maximum speed of the welding platform approached 14 r/min, and the platform could meet the requirements of most welding products. Such a turnover platform can offer the application program of the welding robot with low cost for the middle and low level products, and reduce the cost of welding robot and improve welding productivity.     

Dynamics model and analysis of the lifting system of automatic catwalk北大核心CSCD

When the field test of rope pulled automatic catwalk was carried out, the load fluctuation of rope was obvious, and it was difficult to complete the lifting of the target weight column. Therefore, the structure and motion characteristics of rope pulled automatic catwalk were analyzed, and dynamic model based on the D'Alemebert principle was established, MATLAB software was used to analyze the influence of the distance between the block on the base and the bottom of the ramp, the hinge position of the transfer arm and the support arm, and the length of the support arm on the load of rope. The analysis results showed that adjusting the position of block on the base to the bottom of the ramp, and reducing the length of support arm could reduce the required force of rope in the process of lifting. According to the analysis results, the structure size of automatic catwalk was adjusted to carry out the field test, the test result showed that the maximum lifting oil pressure of the hydraulic which was decreased by more than 2 MPa, the lifting capacity of automatic catwalk was improved. The analysis and experimental results can guide the design and optimization of rope pulled automatic catwalk.     

The effects of handling and storage on magnesium based implants — First results

The present work aimed to investigate the influence of acetone and formalin as well as the duration and type of storage on magnesium based implants by means of microscopic, μ-computed tomographic, scanning electron microscopic, EDX and metallographic investigations.In contrast to storing in acetone, storage in formalin led to an increase in surface to volume ratio, and a decrease of the volume and the density. The various types of storage exerted no differing effects on the implants but with increasing storage duration, a spreading of oxygen rich areas on the surface, increased precipitations and a decrease in grain size could be observed.     

Effect of graphite/sodium nitrate ratio and reaction time on the physicochemical properties of graphene oxide北大核心CSCD

Graphene oxide (GO) was synthesized by the reaction of graphite with sodium nitrate and the graphite/sodium nitrate mass ratio and the reaction time were varied in order to obtain the highest oxygen content. The GO was characterized by TEM, SEM, AFM, XRD, FT-IR, TGA, elemental analysis, and UV-vis and Raman spectroscopy. The effect of oxygen content on the physicochemical properties of GO was investigated. Results indicate that increasing the graphite to sodium nitrate ratio increases the oxygen content, BET surface area, pore volume and pore size but reduces the crystallite size of the GO samples. However, the oxygen content of GO is not directly related to the reaction time. Physicochemical properties such as d-spacing and defect density increase with increasing oxygen content while the thermal stability decreases. The physicochemical properties such as oxygen content, crystallinity, thermal stability and structure can be tailored by. varying the graphite/sodium nitrate ratio and reaction time.     

Damping force modeling and sensitivity analysis of double-tube hydraulic damper北大核心CSCD

In order to improve the accuracy of the damping force's output and performance reliability of the damper, the influence of size and tolerance of the double-tube hydraulic damper and the viscosity of the oil on the damping force is quantitatively analyzed. According to the generation mechanism of the damping force, the damping force model before and after the recovery valve opened in the recovery stroke and the damping force model before and after the compression valve opened in the compression stroke were established. By using the MATLAB simulation, the indicator diagram and speed characteristics diagram were obtained, and the performances were verified by bench test. The sensitivity analysis of the different parameters was done by using the Design Exploration module of ANSYS considering the complexity of model. Based on the randomness of the oil viscosity, the opening degree of the recovery (compression) valve which has more influence on the damping force, the prior distribution of the damping force was calculated by using Monte Carlo method. The results show that the damping force is distributed normally, and the method provides a basis for the design of double-tube hydraulic damper.     

Research on a two-stage iterative model of coupling design task with single input and multiple output北大核心CSCD

In the process of product development, there is a complex information-dependent relation between coupling design tasks with single input and multiple output. Because of the large amount of executed tasks and transmitted information, the complicated relationship between these tasks is hard to be sorted out by using the single-stage task execution method, which may lead to problems such as the unreasonable allocation of tasks in the process of task execution, excessive iteration rework times between tasks and too long product development cycle. To solve these problems, an information processing strategy for the task iteration was put forward, and a two-stage iteration model and the mathematical model of calculating task execution time were built based on the deep analysis of a single-stage iteration model for the coupling design task with single input and multiple output. The best two-stage task allocation scheme was obtained by working out this mathematical model. The effectiveness of this method was proved through the example of an engine development project. The results showed that the iterative execution time of tasks was shorter than single-stage by using the two-stage iteration model and the shortest iterative execution time of the two-stage iteration model could be obtained by reasonably assigning tasks into two phases. The method selects the appropriate task iterative model according to the different information relations between tasks, which can effectively shorten the product development cycle and provide some theoretical reference for product designers to choose reasonable task execution way in the process of product development.