Zeal Press
Not a member yet
427 research outputs found
Sort by
The Effect of Temperature on the Creep Ageing Characteristics of Al-Li Alloys
Full text linkAbstract: In this paper, the evolution of creep strain and mechanical properties of 2195 Al-Li alloy is investigated at different temperatures (160/170/180°C), with the aim of discovering the mechanism of temperature influence on creep properties and providing a reference for improving the creep properties of the target material by adjusting the temperature in the future. This study demonstrates that the creep curve is strongly influenced by temperature, with a plateau and a transition period occurring at low temperatures. As the temperature increases, the creep curve gradually reverts to the typical two-stage creep characteristics due to the interaction of dislocation density proliferation and dislocation reversion within the material at high temperatures. In addition, by means of tests such as TEM, it was confirmed that the decrease in mechanical properties of the material caused by increasing the creep temperature is mainly due to the coarsening of precipitates and the appearance of precipitation-free zones at grain boundaries
Impact of DLC Coating Deposition on the Fatigue Strength of Al-7075-T6 Aluminum Alloy
Full text linkAbstract: Al-7075 has interesting mechanical properties but is susceptible to corrosion. Physical Vapor Deposition (PVD) of coatings results in good corrosion resistance and compressive stresses of the order of 1 GPa on the surface of metallic components. However, the impact of PVD films on the strength of Al-7075-T6 is uncertain. This paper provides a summary of the findings of the Authors’ research group in recent years on the fatigue behavior of Al-7075-T6 with and without PVD Diamond-like Carbon (DLC) coating. The results indicated that DLC-coated specimens have lower fatigue strength than uncoated specimens for lives up to about 10000000 cycles. The failure mechanism was determined by observation of the fracture surfaces of the failed specimens. The stress analysis performed confirms the experimental observation, with crack nucleation expected below the surface of coated specimens, where the highest tensile stresses occur during fatigue loading
Prediction on MRAM Etching Endpoint by Response Surface Method
Full text linkAbstract: STT-MRAM (Spin-Transfer-Torque Magnetic Random Access Memory) with high-density is considered as one of the most promising storage candidates with potential applications. In the process of MRAM manufacturing, etching step should be stopped precisely at the specific material layer. The dielectric layer should be protected with certain coverage. Then the subsequent etching steps continue. It is crucial to detect the endpoint of the etching during the fabrication process.
In the paper, the factors influencing the etching rate are analysed, including gas pressure, gas temperature, ion sheath thickness, self-biased DC voltage and RF power frequency, respectively. An approach based on Response Surface Method (RSM) is adopted to predict the endpoint of the etching process. The optimized interplay relationship is set up among the gas pressure, the gas temperature, the ion sheath thickness, the self-biased DC voltage and the RF power frequency, et al.. It shows that RSM approach is an effective statistical method for the optimization on the etching stop technology, especially when the complex etching condition options are involved. The simulation results demonstrate the MRAM sidewall smoothness can be improved under the optimized etching environment configuration
Small Sample Data-Driven Method for Interval Prediction on Structural Responses
Full text linkAbstract: This paper proposes an approach of intervals prediction on the structural responses under the limited samples by using Grey-BP neural networks (GBP) and genetic algorithm (GA). For the response prediction of complex structures, the presented method can ensure the necessary accuracy and can greatly reduce the cost of computation. Meanwhile, the method is different from the other traditional neural networks, which represents the superiority of dealing with the interval prediction under limited samples with help of the grey theory. In this paper, the Grey-BP neural networks are established by introducing the grey theory, which is used to achieve the mapping relationship between input and output of the system and accomplish the approximation of real mapping. The accuracy of built the mapping model can be tested by error analysis. Subsequently, the issue of interval prediction can be translated to optimal problem for extremum value. Although the explicit expression of the established mapping relationship is unknown, the fitness of every value includes the information of extremum. So, the best fitness and worst fitness can be searched in the given bound of uncertain variables based on genetic algorithm, and then achieve the upper bound and lower bound of the system response depending on the capability of global search. After proposed technologies are given in detail, one numerical example and one engineering example are presented and the results are discussed with common methods based on traditional BP neural network and Monte Carlo, which demonstrates the validity and reasonability of the developed methodology
Mathematical Model of Anal Canal for Anal Fistula Surgery
Full text linkAbstract: Purpose: Surgery is necessary for the treatment of an anal fistula. However, excision of some sphincter muscle would compromise sphincter integrity or function, which is the cause of a reduced success rate in the long term. In order to develop an appropriate surgical plan, a mathematical model that describes the relationship between the internal pressure of the anal canal and the structure of anal sphincters is required.
Methods: The anatomical structure of the anal canal and the corresponding sphincter pressure can be measured by endoanal ultrasound (EAUS) imaging and manometry, respectively. Length-tension relationships for skeletal and smooth muscles, two major components of the external and internal anal sphincter, respectively, were reviewed first.
Results: Based on the information about the internal and external sphincters, two mathematical models, the thick-wall cylinder model and the two-layer model, have been created, from which the influence of complete or partial excision of the sphincter muscle can be estimated.
Conclusions: The proposed thick-wall cylinder and two-layer models could describe the relationship between the internal anal canal pressure and the structure of anal sphincters, from which the influence of complete or partial excision of the sphincter muscle may be estimated
Design of Crop Irrigation Decision-Making System Based on ZigBee Technology
Full text linkAbstract: To promote the high-quality development of agriculture, meet the needs of agricultural products grown in greenhouses, and achieve precise monitoring of greenhouse plants, a small greenhouse micro-environment multi-parameter monitoring system was designed and implemented. The system consists of three parts: a monitoring node, a gateway node, and a remote management platform. The monitoring node used the ESP32 microcontroller as the main control chip, combined ZigBee technology, and embedded different sensors to complete the collection and transmission of environmental parameters. In the gateway node, the 4G Data Transfer Unit module was used as the carrier, and the communication protocol was used to realize data communication between the monitoring terminal and the gateway. The remote management platform was based on the PyCharm development platform. It used the PyQt5 graphical user interface (GUI) toolkit to complete the design of the host computer monitoring platform, establish a database, and realize the storage and analysis of environmental parameters. The remote management platform embedded the crop reference evapotranspiration, online calculation model, to provide irrigation decisions for greenhouse crop management and improve the applicability and accuracy of irrigation decisions. After the experimental test platform was built to test the system communication distance, communication reliability, control reliability, and data reliability, the small greenhouse micro-environment multi-parameter monitoring system designed in this paper can operate stably for a long time. Its functions meet the expected requirements and are in line with modern requirements for multi-parameter monitoring of smart greenhouses
Method of Sensor Fault Identification Based on High-order Sliding Mode Observers
Full text linkThe problem of sensor fault identification in technical systems described by linear equations under the external disturbances is studied. To solve the problem, sliding mode observer is used which is constructed based on the reduced-order model of the original system. This model is sensitive to the faults and insensitive to the disturbances. It is shown that if some conditions are met, then sliding mode exists which allows obtaining exact estimation of the fault
Detecting Magneto-Optical Interactions in Nanostructures
Full text linkEffects due to magneto-optical interactions are responsible for most of the phenomena discovered in optoelectronics and spintronics. Magneto-optical interactions can generate elementary excitations of the order of light-magnetic matter, which can flow under certain conditions. Here, we observe the intensities of magneto-optical interactions in hexagonal arrays of magnetic nanowires using experimental measurements and simulations. Nanowires of three materials (cobalt-Co, iron-Fe, and nickel-Ni) were electrodeposited on alumina membranes by the AC electrodeposition method. Our results reveal that the magneto-optical behavior can produce, under certain conditions, a kind of avalanche of magneto-optical interactions, which is dynamic. Such an observation shows the possibility of generating a magneto-optical current (spin-opto current)
Seepage Analysis Beneath Gravity Concrete Dam Using Flow Net Method and PLAXIS 2D
Full text linkDam is a hydraulic structure that built across a river that construct especially for water supply, flood control, energy production, irrigation, recreation, and other. Many problems can occur on the dam construction such as seepage problem, which is seepage need to be controlled in purpose to meet the community’s requirement. In this study, the design and seepage analysis of the construction of a dam built on a river with spanning 400 meters which has a water height of up to 12 meters were carried out. The selection of the solution was obtained based on a numerical method using PLAXIS 2D and analytical analysis with the flow net method of seepage discharge Based on the analysis results, the best solution is obtained by making a dam design that suits the needs where the dam is made with a width of 20 m and a height of 20 m and with the addition of a cut-off structure at the foot of the dam on the left and right sides to a depth of 18 m so that the seepage discharge that occurs in less than 500 m3/day which is meet the community’s requirement. This result indicate that a cutoff wall beneath the dam can reduce and control the seepage on a hydraulic structure, but to design the dam with cutoff wall a couple of analysis need to do to predict the seepage which is with the analysis the seepage problem can be handled
Development of Control Method for Abration and Evaluation of Electrocautery Device Controller
Full text linkThe symmetrical impedance bridge, will be suggested to yield consistent and reliable results for measuring tissue damage during electrosurgical ablation. The methods that were identified as potentially viable for ablation detection were force and displacement measurements between the electrode tip and tissue surface. These were found to correlate tissue damage due to a high degree of variability in charge density caused by contact area variation. Another method, temperature measurement via thermistors, will be found to have a response time and a non-contact method will be examined with the size constraints. The last method will be to measure and correlate changes in the power output of the ESU to tissue damage. This method will be practically examined to measure and correlate to tissue damage due to ESU power output modulation. The changes in the tissue\u27s electrical properties can be measured directly far more easily than measuring the power output. Correlation with tissue damage tended to be strong with an error range below what can be detectable by the human eye. But the high degree of variability in the mechanical properties of tissue makes the use of force and displacement measurements difficult to implement as part of a control method for ablation control