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  • 1
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    Recrystallization behaviour of AA6063 extrusions (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-08-08
    Description: Cylindrical profiles of an AA6063 aluminium alloy were produced in a lab-scale direct extrusion set-up. The extrusion was performed at 300 ?C, 450 ?C and 550 ?C, respectively, with the same ram speed. Immediate water quenching was applied to the profiles and the end of billet (butt-end) after extrusion. Microstructure and texture of the material in different states were measured by electron back-scattered diffraction. Only the profile extruded at 300 ?C, was found in the deformed state after extrusion, featuring a fibrous grain structure and a strong and weak double fibre texture. Post-extrusion annealing of this profile at 450 ?C resulted in an almost fully recrystallized structure (recrystallized fraction of 87%) and with a texture similar to that of the as-deformed state. The profile extruded at 450 ?C was almost fully recrystallized (recrystallization fraction 91%) already after quenching, and with a texture characterized by a weak and stro...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 2
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    Research of nanocomposite structure of boron nitride at proton radiation (2016)
    Institute of Physics (IOP)
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    Publication Date: 2016-02-24
    Description: Using roentgen diffraction and electron microscopy, the influence of nanosecond irradiation by ion beams of high energy on forming of self-organized nanoblocks in near surface's layers of boron nitride (BN) has been studied. It was shown that low temperature transitions from hexagonal to wrutz boron nitrides is associated with changes of shape and sizes of self-organized particles consisting the nanoblocks. We have calculated the parameters of nanoblocks using the meanings of interplane distances and properties of subreflexes orders. The collective shifting deformations of layers in nanoblocks provides phase transition under the screen and forming the set of nanotubes with escaping of five order axes of symmetry. It has been realized that pentagons and stars arranged in points of entrance of five order axis of symmetry are associated with peculiarity of self-organization of the spiral-cyclic structures.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 3
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    Energy efficiency test and analysis of large hydro-generators based on economic evaluation (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-07-31
    Description: A new evaluation method was proposed for the determination of economic operation zone of large hydrogenerators. Firstly, a large number of test data were obtained by carrying out efficiency tests of the turbine at different heads. Secondly, through data analysis, the value method of K 0 and the water consumption rate were constructed to determine the economic operation zone and the optimal economic operation zone, separately. Thirdly, the validity of the proposed method was verified by applying to an actual hydrogenerator. Compared with traditional methods, this method can be used to guide the economic operation of hydropower plants.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 4
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    Evaluating Gravity-Assist Range Set Based on Supervised Machine Learning (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-11-30
    Description: The dynamics of gravity-assist (GA) trajectories contain strong nonlinearity, which makes the traditional methods for impulse transfer range set (RS) are intractable to deal with the gravity-assist RS. This paper develops a novel method to evaluate the gravity-assist RS based on regression methods in supervised machine learning (SML) field. The performances of three powerful regression methods with several common kernel functions are assessed. The Gaussian Processes Regression (GPR) method with Matérn 3/2 kernel is selected because of the minimum mean squared error (1.11×10 −3 km 2 /s 2 ). The predicting model based on GPR is constructed to make prediction form the orbital elements of destination orbits to the total velocity increment of corresponding optimal GA trajectories. The percentage error of predicting model is no more than 2%. Millions pairs of sample points are generated by the trained predicting model. The points with specified value of tot...
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
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    Control method of shaft and hole mating based on convolution neural network in assembly building prefabricated components (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-09-20
    Description: In order to further improve the automation degree of assembly building construction, realize prefabricated component intelligentized positioning, this paper applies the convolutional neural network in positioning control in the field of prefabricated component of assembly building, and puts forward a probability search into target region to establish a new method for loss equation algorithm, the method based on multi label classification loss equation modelling with probability search algorithm, in the training process to continuously improve the positive incentive probability score. The simulation results show that the designed convolution neural network can achieve a correct prediction of the assembly location control instruction, and the proposed method can improve the prediction accuracy and convergence of the network model.
    Print ISSN: 1757-8981
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
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    The dynamic stability analysis of telescopic booms of the crane based on the energy method (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-09-20
    Description: According to the energy method, the dynamic stability of a crane’s telescopic boom under the periodic load is studied, which is known as parametric resonance, based on the design code for a crane (GB/T3811-2008), the stability analysis model of the box telescopic boom can be regarded as variable-section stepped columns. The parametric vibration equation of n-stepped columns which expressed as Mathieu Equation is deduced by the Hamilton Principle, then the Critical frequency equation of dynamic instability regions of the telescopic booms are derived, finally, the effects of damping to the dynamic stability of telescopic boom are discussed. The results show that, the dynamic instability regions are reduced when the damping coefficient is increased and the effect on the second dynamic instability region is more obvious, that means damping improves the structure’s dynamic stability.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
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    Correlation between nebkhas formation ability and silhouette layer parameters of desert plants (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-11-06
    Description: To determine why certain desert plants form nebkhas whereas others do not, we investigated common sand-fixing plants of the Minqin desert region, with 108 plants and nebkha samples set up at the edge of the above region. Measurement and comparative analysis of markers such as silhouette layer width, area, and center height revealed the following trends: (i) The silhouettes of nebkha-forming plants are triangular or cylindrical, i.e., the width of these silhouettes decreases with increasing height, and the silhouette centers are positioned 30 cm above the ground. Thus, these plants are shrubs. Plants that do not accumulate sand to form nebkhas are rhombus-shaped, and their silhouette centers are located more than 30 cm above the ground. (ii) Drifting sand flux and sandstorm particles are mainly concentrated in the region between 0 and 30 cm above the ground, explaining why plants with lower silhouettes can easily accumulate sand to form nebkhas. (iii) After being buried in sand, ...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 8
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    Simultaneously Toughening and Strengthening of PLA-b-PCL Copolymer via Pressure-induced-flow Processing at Room Temperature (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-24
    Description: Biodegradable but brittle polylactide (PLA) can be toughened by copolymerizing with poly caprolactone (PCL). However, the tensile strength and Young’s modulus dramatically decrease compared with pure PLA. On the other hand, melting processing is normally applied for most plastics at relatively high temperatures and may lead to substantial degradation of polymers like PLA-b-PCL copolymer. In this study, we adopted pressure-induced-flow (PIF) processing to manufacture PLA-b-PCL copolymer specimens at room temperature of ∼30 °C. Impact toughness, tensile strength and Young’s modulus were simultaneously increased by about 190 %, 151 % and 107 % respectively, when compared with the samples processed via injection moulding. We attributed the remarkable improvements to the multi-layered morphologies generated during PIF-processing which are parallel to the flowing direction. Moreover, the molecular weight and all mechanical properties for PLA-b-PCL were well preserved at such low proce...
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  • 9
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    Research on Coordinated Development Strategy of Northeast Power Grid and National Energy Grid (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-06-16
    Description: In the new era, the Northeast power grid is facing a series of opportunities and challenges. In this paper, the strategy of “complementary”, “transmission” and “mutual benefit” coordinated development of Northeast China Power Grid and national energy grid is formulated based on the relevant national policy planning; Considering the difference of unique geographical location, natural resources, human resources, technology and other factors of the northeast and other areas; taking into account the development situation and future development needs of all regions, formed a coordinated development strategy layout, covering the unified planning, new energy development, peaking capacity construction, power substitution and talent support. It is beneficial to improve the efficiency of the national energy allocation and utilization, and to solve the practical problems faced by the power grid, so as to realize the coordinated development of the Northeast Power Grid and the national energ...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
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    Stability mechanisms of barchan dunes: A case study of Hexi Desert area in Gansu Province (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-09-01
    Description: Barchan dunes, an important type of dunes, are distributed on the edge of oases. Research of stability mechanisms of barchan dunes is of great importance to the determination of regulation of aeolian sand movement on the edge of oases. However, the stability of barchan dunes remains an unresolved scientific issue. In this paper, the stability mechanisms of the top of barchan dunes in Hexi desert area of Gansu Province were analyzed. The results showed that: (1) in Hexi desert area of Gansu Province, patches of barchan dunes were distributed downwind on the edge of desert. The distribution areas were flat sandy-clay or sandy-gravel beaches. The lowlands among the dunes were wide and had the prominent prevailing wind. (2) The prevailing northwestern wind caused the highest point and sand ridge line of the dunes to coincide, and the dunes to move forward and become lower. The southeastern wind (opposite to the prevailing wind) caused the highest point and sand ridge line of the dun...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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