Hasil untuk "Mechanical engineering and machinery"

Emil Mihai Pavelescu, Saroj Kumar Patra, Cosmin Romaniţan et al.

Intermediate band solar cells (IBSCs) have the potential to overcome the efficiency limit of single-bandgap solar cells. Dilute nitride III–V alloys, with splitting of the conduction band due to band anticrossing, can be used as the intermediate-band material for solar cell applications. In this work, we report on the introduction of engineered GaInNAs alloy, with low (dilute) In and N contents, as IBSC material and the comparison of the performances of GaInNAs-based and the corresponding In-free GaNAs-based IBSCs grown on GaAs (100) substrate. Introduction of a small amount of In (3%) in a GaN _0.011 As _0.989 -based IBSC was found to noticeably increase the short-circuit current, I _sc , at the expense of a small decrease in the open-circuit voltage, V _oc . When annealed at 750 °C for 90 s, significant enhancements in I _sc and V _oc are seen, especially in the In-containing solar cell. The observed In-related enhancement in cell parameters after annealing is related to In-promoted bandgap tailoring and efficient curing of carrier traps during annealing. This occurred without change in the macroscopic composition of the GaInNAs alloy, most likely by In-N bond formation upon annealing, a phenomenon which does not exist in the GaNAs alloy.

Haoran Liu, Huaqiang Li, Xueying Yu et al.

Abstract The volatility of renewable energy generation impacts the safe and stable operation of power systems. Moreover, load uncertainty complicates renewable energy consumption. Therefore, accurately extracting load patterns using artificial intelligence (AI) technology is crucial. Load classification is an effective way to master load behaviour. However, issues in the collected load data, such as data class imbalance, significantly affect the accuracy of traditional load classification. To address this problem, this study proposes a novel classification method based on data augmentation and few‐shot learning, significantly enhancing the training efficiency of algorithm recognition. This addresses the challenge of real‐data recognition in power systems. First, time‐series load data are converted into images based on the Gramian angular field method to extract time‐series data features using a convolutional neural network. Subsequently, the data are augmented based on variational autoencoder generative adversarial network to generate samples with distributions similar to those of the original data. Finally, the augmented few‐shot data are classified using the embedding and relation modules of the relation network. A comparison of the experimental results reveals that the proposed method effectively improves power load classification accuracy, even with insufficient data.

Doaa Eid, Said Elmasry, Adel El Samahy et al.

Renewable energy sources (RESs) are considered a crucial energy transformation to reduce carbon emissions, so more RESs are being integrated into contemporary power systems. Power electronic converters are extensively utilized to connect power grids with renewable generators to manage the fluctuations and unpredictability of these renewable energy sources. This paper introduces a multi-terminal multi-function inverter (MT-MF) designed for a battery energy storage system (BESS) to maintain the frequency stability of a hybrid microgrid (MG). The MG comprises a photovoltaic generation system, a diesel generator, BESS, and two loads: one constant load and the other variable, fed through a medium-voltage radial feeding system. An introduced approach involves utilizing a model predictive control controlled virtual synchronous generator (MPC-VSG) for BESS. This method offers inertia support during transient states and improves the dynamic characteristics of system frequency. In addition, it enables the connection of multiple batteries, provides individualized control for each, and supports the injection of reactive power into the MG. The required power from the BESS is shared between the two batteries using the low pass filter technique. The simulation outcomes affirm the proposed control strategy’s effectiveness and underscore the MT-MF inverter approach’s potential in integrating extensive RESs. This paper also explores how the proposed technique outperforms other methods in improving frequency stability.

Xinyi Kong, Jianwen Zhang, Jianqiao Zhou et al.

The bipolar low-voltage DC (LVDC) distribution system has become a prospective solution to better integration of renewables and improvement of system efficiency and reliability. However, it also faces the challenge of power and voltage imbalance between two poles. To solve this problem, an interface converter with bipolar asymmetrical operating capabilities is applied in this paper. The steady-state models of the bipolar LVDC distribution system equipped with this interface converter in the grid connected mode and off-grid mode are analyzed. A control scheme based on DC offset injection at the secondary side of the interface converter is proposed, enabling the bipolar LVDC distribution system to realize the unbalanced power transfer between two poles in the grid-connected mode and maintain the inherent pole voltage balance in the off-grid mode. Furthermore, this paper also proposes a primary-side DC offset injection control scheme according to the analysis of the magnetic circuit model, which can eliminate the DC bias flux caused by the secondary-side DC offset. Thereby, the potential core magnetic saturation and overcurrent issues can be prevented, ensuring the safety of the interface converter and distribution system. Detailed simulations based on the proposed control scheme are conducted to validate the function of power and voltage balance under the operation conditions of different DC loads.

Chengliang Zhang, Guanlei Gao, Chunzhao Zhao et al.

This paper presents a path tracking algorithm based on a fuzzy control pure tracking model for autonomous navigation of 4WS agricultural machines. The aim of this research is to implement path tracking for unmanned 4WS agricultural machinery and to solve the problem of difficult determination of forward-looking distances in pure tracking algorithms. By using the pure tracking algorithm model and a fuzzy controller, this paper converts the heading deviation and lateral deviation in one control cycle into the sum of lateral deviation as the first input to the fuzzy controller and the vehicle travel speed as the second input to the fuzzy controller, thus outputting the actual forward-looking distance. In order to verify the practicality, accuracy, and path tracking precision of the proposed path tracking algorithm, a straight-line path tracking test under variable speed conditions and a turning path tracking test under non-fixed forward-looking distance conditions were carried out using a test platform after simulation on MATLAB/Simulink in this paper. The test results show that: in the straight-line path tracking process, the maximum overshoot is 0.123 m, and after stable driving, the maximum lateral deviation of the straight-line tracking part is 0.058 m and the steady-state deviation is 0.039 m; in the bow-turn path tracking process, the absolute value of the maximum lateral deviation of the actual driving trajectory of the farm machine from the desired path is 0.139 m, and the average tracking deviation is 0.041 m. It can be seen that the path tracking control algorithm proposed in this paper has good tracking accuracy as well as convergence, and can meet the demand for the autonomous navigation function of 4WS agricultural machinery, which has a certain application value.

Guizhen Du, Xianshan Dong, Xinglong Huang et al.

Vacuum packaging is used extensively in MEMS sensors for improving performance. However, the vacuum in the MEMS chamber gradually degenerates over time, which adversely affects the long-term performance of the MEMS sensor. A mathematical model for vacuum degradation is presented in this article for evaluating the degradation of vacuum packaged MEMS sensors, and a temperature-accelerated test of MEMS gyroscope with different vacuums is performed. A mathematical degradation model is developed to fit the parameters of the degradation of Q-factor over time at three different temperatures. The results indicate that the outgassing rate at 85 °C is the highest, which is 0.0531 cm²/s; the outgassing rate at 105 °C is the lowest, which is 0.0109 cm²/s; and the outgassing rate at 125 °C is in the middle, which is 0.0373 cm²/s. Due to the different mechanisms by which gas was released, the rate of degradation did not follow this rule. It will also be possible to predict the long-term reliability of vacuum packaged MEMS sensors at room temperature based on this model.

HE DongTai, GUO Yu, WU Xing et al.

To multi-faults of a gearbox, the strong fault feature vibration of gearing always interfered with rolling element bearing weak fault vibration. The traditional methods are difficult to extract the weak bearing fault feature. In order to solve the problem, a vibration analysis scheme for multi-faults vibration of gearbox based on discrete random separation（DRS） is proposed. In the proposed method, the resonance parameters of the gearbox vibration is obtained based on the fast kurtogram algorithm at first, built a bandpass filter that included resonance parameters, and the envelope is extracted by Hilbert transform. Then, converted envelope to the angle domain based on the equi-angle increment resampling to remove speed fluctuation. Next, the SANC is performed to separate the envelope in the angle domain. As a result, the gear fault corresponding envelope component and the bearing fault related envelope component are obtained; Finally, the spectrum analysis is carry out on the two envelope components respectively for the fault diagnosis information. Test results show that this method can be used to extract the gear and bearing fault features effectively.

Kazuki HORIKIRI, Tetsuro YANASEKO, Isao KUBOKI et al.

This paper describes the fabrication of a metal matrix piezoelectric composite using surface-oxidized nickel fiber as the internal electrode. Piezoelectric ceramics, which have excellent piezoelectric properties, are widely used as energy conversion materials. However, their application is limited by their brittleness. To solve this problem, a metal-core piezoelectric ceramic fiber/aluminum composite has been developed by using the interphase forming/bonding method. Here, a piezoelectric ceramic is reinforced by embedding it in an aluminum matrix, and this process causes the piezoelectric ceramic to have better mechanical properties than a bulk ceramic. However, this composite has some serious disadvantages considering that it cannot be designed to possess arbitrary piezoelectric properties because the metal-core piezoelectric fiber is formed by the extrusion method, so that the sectional shape cannot be arbitrarily changed. In this paper, a metal matrix piezoelectric composite using a surface-oxidized nickel fiber as the internal electrode is proposed. This composite provides design flexibility in that its piezoelectric property can be changed by varying the size and materials of the composite. The fabrication procedure of this composite consists of three steps: oxidation of the internal electrode, molding and sintering of the piezoelectric ceramic, and embedding of the piezoelectric ceramic into the metal matrix. The proposed composite is fabricated under optimized oxidizing and molding conditions. An impact test is performed on the fabricated composite, and the output voltage is measured. The test results indicate that the composite is capable of generating piezoelectricity. Overall, the study results substantiate the validity of the concept and fabricating method of the proposed composite.

Xiaoting Huo, Qi Chen, Lei Wang et al.

Separation and concentration of target bacteria has become essential to sensitive and accurate detection of foodborne bacteria to ensure food safety. In this study, we developed a bacterial separation system for continuous-flow separation and efficient concentration of foodborne bacteria from large volume using a nickel nanowire (NiNW) bridge in the microfluidic chip. The synthesized NiNWs were first modified with the antibodies against the target bacteria and injected into the microfluidic channel to form the NiNW bridge in the presence of the external arc magnetic field. Then, the large volume of bacterial sample was continuous-flow injected to the channel, resulting in specific capture of the target bacteria by the antibodies on the NiNW bridge to form the NiNW−bacteria complexes. Finally, these complexes were flushed out of the channel and concentrated in a lower volume of buffer solution, after the magnetic field was removed. This bacterial separation system was able to separate up to 74% of target bacteria from 10 mL of bacterial sample at low concentrations of ≤10² CFU/mL in 3 h, and has the potential to separate other pathogenic bacteria from large volumes of food samples by changing the antibodies.

T. Bessaad, R. Taleb, A. Namoune et al.

Dans ce contexte, le travail présenté porte sur l’étude, la modélisation d’une machine hexaphasée alimentée par un onduleur héxaphasé. Cette machine asynchrone hexaphasée (MASHP) n’est pas un système simple, car de nombreux phénomènes compliqués interviennent dans son fonctionnement, comme la saturation, l’effet de peau, etc..., [1]. L’objectif de ce travail est de présenter le modèle général de la MASHP dans le repère réel (abc). Ensuite, nous présenterons les différentes étapes permettant d’aboutir au modèle diphasé de la MASHP, obtenu à partir d’une matrice de transformation appropriée [2]. Afin de simplifier l’étude, la simulation numérique de la MASHP, le système de dimension six sera décomposé en trois sous-systèmes découplés. Après l’alimentation de la MASHP par un onduleur de tension héxaphasé sera présentée. Dans ce qui suit, nous allons étudier l’influence du changement de l’angle de déphasage sur le comportement de la MASHP et nous avons montré que les meilleures performances sont obtenues pour la configuration =30°.

Alireza Haji Fathaliyan, Xiaoyu Wang, Veronica J. Santos

Human–robot collaboration could be advanced by facilitating the intuitive, gaze-based control of robots, and enabling robots to recognize human actions, infer human intent, and plan actions that support human goals. Traditionally, gaze tracking approaches to action recognition have relied upon computer vision-based analyses of two-dimensional egocentric camera videos. The objective of this study was to identify useful features that can be extracted from three-dimensional (3D) gaze behavior and used as inputs to machine learning algorithms for human action recognition. We investigated human gaze behavior and gaze–object interactions in 3D during the performance of a bimanual, instrumental activity of daily living: the preparation of a powdered drink. A marker-based motion capture system and binocular eye tracker were used to reconstruct 3D gaze vectors and their intersection with 3D point clouds of objects being manipulated. Statistical analyses of gaze fixation duration and saccade size suggested that some actions (pouring and stirring) may require more visual attention than other actions (reach, pick up, set down, and move). 3D gaze saliency maps, generated with high spatial resolution for six subtasks, appeared to encode action-relevant information. The “gaze object sequence” was used to capture information about the identity of objects in concert with the temporal sequence in which the objects were visually regarded. Dynamic time warping barycentric averaging was used to create a population-based set of characteristic gaze object sequences that accounted for intra- and inter-subject variability. The gaze object sequence was used to demonstrate the feasibility of a simple action recognition algorithm that utilized a dynamic time warping Euclidean distance metric. Averaged over the six subtasks, the action recognition algorithm yielded an accuracy of 96.4%, precision of 89.5%, and recall of 89.2%. This level of performance suggests that the gaze object sequence is a promising feature for action recognition whose impact could be enhanced through the use of sophisticated machine learning classifiers and algorithmic improvements for real-time implementation. Robots capable of robust, real-time recognition of human actions during manipulation tasks could be used to improve quality of life in the home and quality of work in industrial environments.

Reshetnikov I.F., Shikhalev S.V., Tikhonov S.L.

The aim of the article is a quantitative assessment of the influence of non-condensable gases on the intensity of heat and mass transfer processes during film condensation of steam in the specific conditions for heat exchanger. The task is achieved by conducting experimental research of heat and mass transfer processes in film condensation of steam in the presence of non-condensable gases.The study was carried out by the method of stationary heat flow on an experimental kettle with a jacket (0,02 m3 capacity), industrial cooking boilers (0,04 m3 and 0,06 m3 capacity). Cylindrical kettles with a hemispherical and elliptical bottom were selected as the condensation surface. The results of the experiments are presented in the form of a criterion equation for determining the mass transfer coefficient for vapor concentration diffusion. When the concentration of a non-condensable gas reaches 40% an intensification of the resulting heat transfer coefficient from the vapor-gas mixture to the condensation surface is observed. The coefficient of heat transfer to the condensation surface depends on the concentration of non-condensable gases in the apparatus cavity. The results of the research indicate that it is possible to improve the heat exchangers with a jacket and allow an assessment of the heat input when removing the gas mixture from the jacket in the heating mode of the cookers at the design stage. Material research allows to develop automatiс systems and control parameters in the operation of apparatus with a jacket.

Azreen Zainol, M.Z.A. Yazid

Turning operations are a versatile secondary metal cutting process. In metal cutting industry, manufacturing processes are designed to attain minimum manufacturing cost, best quality and improved cutting tool's performance. Nonetheless, the deterioration of cutting tools, occupational diseases amongst the workers and environmental aspects are increasingly becoming a major issue. Therefore, one alternative to reduce the impact of metal cutting activity in term of cutting tool, the health and environment is Portable MQL Applicator. The portable MQL applicator is an equipment that equipped with pneumatic system to deliver a small amount of fluid in the form of aerosol into the cutting zone. The effect of the portable MQL applicator was investigated and compared with the results from dry machining in terms of tool life and material removal rate in turning of Inconel 718 using carbide tool. The results showed that the applications of the portable MQL applicator have successfully resulted in better tool life and improved material removal rate.

Randall Spalding-Fecher

One of the most important parameters for developing Clean Development Mechanism (CDM) project proposals in the electricity sector (both supply and efficiency) is the standard electricity ‘grid emission factor’, which represents the carbon dioxide related to a megawatt hour of electricity supplied or saved on the grid. While there are detailed guidelines from the CDM Executive Board on how to calculate this emission factor, the values used in registered CDM projects in South Africa vary widely, both due to changes in the rules over time and also to misapplication of the rules. This paper shows how the application of the latest guidelines gives a ‘combined margin emission factor’ for South Africa of 0.957 tCO2/MWh in 2009/2010. The variation in emission factors in the literature, as well as the importance of reducing the transaction costs for South African project developers, points to the need for an official published grid emission factor from the CDM host country authority in South Africa, the Designated National Authority (DNA), within the Department of Energy.

Liu Xiaole, Liu Houguang, Cheng Gang et al.

Taking two-stage planetary gear of the cutting part of MG900 /2215-GWD shearer as study object,the dynamics analysis simulation of it is carried out by using virtual prototype technology.By comparing the meshing force curves in time domain and frequency domain of the health and several broken tooth fault of varying degrees,the dynamic response of two-stage planetary gear system under fault condition is analyzed.It can be found that under fault condition,the mesh force side bands of energy become intensive,and the intensity increases with the extent of the damage increase.The research results can provide a theoretical basis for two-stage planetary gear fault diagnosis and testing.

V. M. Kryazhkov, Z. A. Godzhaev, V. G. Shevtsov et al.

In the market of agricultural tractors of Russia in 2013 were 900 domestic models, or 3.4 percent. There were produced 7655 tractors, 6707 from which were foreign models. It was revealed that purchasing power of the agricultural organizations appears at profitability not less than 20 percent. Because this indicator is 5.2-11.7 percent lower, agricultural enterprises are not able to turn over their fleets. The authors have presented the forecast of development of tractor fleet till 2020 taking into account the solution of national tasks, including import substitution and dynamics of the annual purchases providing its realization. Methodology of development of the State program of food import substitution based on tractor fleet revival as conditions of self-sustainability of Russia was proposed. A role of tractor fleet as multiplier in development of the mechanized agricultural production was revealed. The first-priority problem is working out of tractors of economic category.

Pengfei Yu, Jinjun Zhang, Bo Yu et al.

Oana CHIVU, Dan DOBROTA, Claudiu BABIS

The present paper is concerned with the main modeling elements as produced by means of thefinite element method of linear ultrasonic motors. Hence, first the model is designed and then a modaland harmonic analysis are carried out in view of outlining the main outcomes

Sudirman -, I Gusti Bagus Wijaya Kusuma, Made Sucipta

Electrical energy available in Indonesia at this time is not yet sufficient for all existing activities, this can be proved byfrequent occurrence of blackouts in several areas in Indonesia. It is necessary for a saving in electrical energy consumptionin all sectors, it is one of the refrigeration system. Research was conducted by testing AC (3 HP / 3 phase) using 2 differentcontrol systems, namely conventional control and FLC. Testing is done by placing the indoor units in cold storage room.Each test performed with varying load in the test room, ie no light burden, lamp 1000 Watt, and lamp 2000 Watt. Testingusing a conventional control system set point temperature 26 ° C and 3 variations of the differential is 1 , 2 and 3 , the FLCusing the temperature setting point 26 ° C. From this research we can conclude that the application of FLC system produceselectric energy consumption of the lowest compared to conventional control in this case is the differential 1. FLC applicationof electrical energy consumption at load 1000 Watt lower 11% and the load 2000 Watt 4% lower compared withconventional control in diffrensial 1.