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Engineering analysis method of diluted magnetic semiconductor system and its application

Diluted magnetic semiconductor (DMS) combines the charge transport characteristics of semiconductors with the information storage characteristics of magnetic materials, and is the key material to construct a new generation of spintronic devices. Due to the introduction of magnetic elements, diluted magnetic semiconductors have a series of characteristics different from ordinary semiconductors. Diluted magnetic semiconductors can manipulate the charge and spin of electrons at the same time, which increases the freedom of electrons and greatly improves the transmission rate of magnetic storage, thus attracting the attention of many researchers. Diluted magnetic semiconductor is the focus of international research, and ZnO-based diluted magnetic semiconductor is one of the most striking ones. At present, most ZnO doped with transition metal (TM) has been reported to be ferromagnetic, among which ZnO doped with Co, Ni or Mn is the most widely studied. Although a lot of progress has been made, there are still many problems to be solved (such as the magnetic origin of ZnO: TM, whether ZnO: TM can show intrinsic ferromagnetism, etc. In this paper, ZnO semiconductor samples doped with different concentrations of transition metals were prepared by magnetron sputtering. A variety of ZnO semiconductor systems doped with different transition metals were studied. The structure, optical and magnetic properties of ZnO-based semiconductors caused by transition metal doping were studied in detail by means of SQUD, XRD and XPS. The existing mode of transition metals in ZnO matrix was analyzed, and the ferromagnetic mechanism was discussed, with emphasis on ZnO: V thin films. 1. ZnO: TM (V, Mn, Fe, Co, Ni) thin films were prepared by DC reactive magnetron sputtering, and their structure, optical and magnetic properties were studied. The results show that all the films have wurtzite structure. When the doping concentration is low, the film grows along the C axis. With the increase of doping concentration, some films become amorphous while others remain polycrystalline. This is because different ion radii lead to different lattice distortions. The transmittance of ZnO: V and ZnO: Fe films first decreases and then increases with the increase of doping concentration, while the transmittance of ZnO: Ni and ZnO: Co films decreases with the increase of doping concentration. 2. Among ZnO: TM (V, Mn, Fe, Co, Ni) films, only ZnO: V and ZnO: Mn films have room-temperature ferromagnetism, while others have no room-temperature ferromagnetism. Preliminary analysis shows that the ferromagnetism of ZnO: Mn and ZnO: V films comes from the bound magnetopolaron formed by doped ions and defects in the films. The radius of doped ions and defect concentration will affect the formation of bound magnetopolaron in thin films to varying degrees. 3. ZnO: V series samples were prepared under different conditions, and the effects of total pressure, oxygen bias and substrate temperature on the structure and characteristics of ZnO: V thin films were studied. 4. In order to prove that the ferromagnetism in thin films is related to the defect concentration, this paper studies the effect of annealing on the ferromagnetism of thin films. The results show that when the annealing temperature is lower than 500℃, the wurtzite structure of ZnO thin films will not change due to annealing. However, the crystal is improved, the grain size is gradually increased and the stress is gradually released, which makes the transmittance of the film increase with the increase of annealing temperature. After vacuum annealing, the ferromagnetic properties of the films are enhanced, and the saturation magnetization increases with the increase of annealing temperature. The saturation magnetization of the films annealed at 500℃ is about twice that of the films without annealing. However, films annealed in air do not have room temperature ferromagnetism. 5. ZnO thin films with different V doping concentrations were prepared on silicon substrate. When the doping concentration is small, the film has a high C-axis orientation. With the increase of doping concentration, the intensity of (002) peak gradually weakens. The crystallization quality of thin films with the same doping concentration on silicon substrate is better than that on glass. The ferromagnetism of thin films on Si substrate has the same trend as that of ZnO: V thin films prepared on glass, but its saturation magnetization is small, which shows that the ferromagnetism in thin films is related to its defect concentration. 6. The electronic structures of wurtzite ZnO and ZnO: Mn are studied by using the ultra-soft pseudo-potential energy band calculation method of density functional theory. According to the previous experimental results, Mn in the film is tetravalent Mn4+, and O2- is removed to maintain electrical neutrality. Theoretical calculation shows that the band gap of ZnO: Mn increases with the increase of doping concentration, and the doping of transition metal Mn leads to the formation of spin-polarized impurity energy levels. The total density distribution of spin-up and spin-down electrons is different, which is asymmetric and ferromagnetic.

Inverter welding machine

Urban engineering geological environment is a complex system. Its complexity is mainly manifested in its dynamic characteristics under internal and external factors, especially human economic engineering activities, and a series of difficulties it brings to the current situation evaluation and trend prediction of urban environmental engineering geology. This paper discusses the environmental engineering geological problems caused by internal and external causes. From the perspective of system engineering and knowledge engineering technology, this paper probes into the basic ways of urban environmental engineering geology. Firstly, the necessity and importance of guiding urban environmental engineering geology research with system engineering are expounded. Secondly, taking Anshan City, Liaoning Province, Tonghuan City, Shanxi Province and Nantong City, Jiangsu Province as examples, the methods of urban environmental engineering geological analysis, numerical simulation, quality evaluation and prediction based on system engineering and computer technology are introduced in detail. Seismic hazard analysis and simulation study of site earthquake disaster effect in Anshan city, Tongchuan environmental engineering geological quality zoning and geological disaster trend prediction system, urban environmental engineering geological gray prediction and urban planning analysis. A computer-aided work system with multiple functions of data analysis, graphic analysis and comprehensive evaluation has been successfully developed. Through the above research, the technical ways and methods of environmental engineering geology in different cities are discussed, and some useful suggestions are put forward, which can be used to guide the management of urban environmental engineering geology and the urban planning of three cities.

Analysis method of urban environmental engineering geological system engineering and its application Read the whole book online and download it in chapters and pages. This system does not support download tools such as Thunder or FlashGet for the time being.

Systematic engineering analysis method of urban environmental engineering geology and its application.

Author Jia Jialin;

Tutor Hu Haitao; Ha chengyou;

Degree awarding unit: Chinese Academy of Geological Sciences;

Name of discipline and specialty engineering geology

Degree year 1992

Doctoral degree

Online publishing feed: Chinese Academy of Geological Sciences

Submission time of online publication 2007-12/20

The engineering geological environment of a city is one of the complex systems monitored by the Institute of Urban Development. Its complexity is mainly manifested in the dynamic change characteristics under the internal and external dynamics of the system, especially under the action of human economic-engineering activities, and the obstacles brought by people's evaluation and prediction of the present situation and development trend of urban environmental engineering geological quality and the formulation of effective disaster prevention and environmental management measures. In this paper, the environmental engineering geological problems caused by internal and external dynamic factors acting on the city are taken as the research object, and the basic ways to carry out urban environmental engineering geological work are discussed emphatically from the methodology by applying the research methods of system engineering and knowledge engineering. Firstly, the inevitability and necessity of applying system engineering to guide urban environmental engineering geology research are expounded theoretically. Taking Anshan, Liaoning Province, Tongchuan, Shaanxi Province and Nantong, Jiangsu Province as examples, this paper expounds in detail the concrete methods of applying system engineering theory and computer technology to environmental engineering geological analysis, mathematical simulation, environmental engineering geological quality evaluation and prediction. Completed the analysis of urban seismic risk and simulation of earthquake damage effect in Anshan, the systematic prediction of urban environmental engineering geological quality zoning and urban geological disaster development trend in Tongchuan, the grey prediction of urban environmental engineering geological quality in Nantong and the suitability analysis of urban planning, established a computer-aided work system for data analysis, graphic processing and comprehensive evaluation, and explored the technical routes and methods of different types of urban environmental engineering geological research, which is the engineering geological ring of the three cities. ...

Urban engineering geological environment is a complex system. Its complexity is mainly manifested in its inherent dynamic characteristics. And a series of difficulties in the evaluation and trend prediction of urban environmental engineering geology caused by this. This paper discusses the environmental engineering geological problems caused by internal and external causes. From the point of view, ...

Updated on March 28th, 2008.

Nantong, geological environment, land subsidence, geological system, engineering geological research, urban environment, Jiang 'an, Tongchuan, Anshan, environmental engineering.

System engineering method and its application

Author: Hao Yong

ISBN: 10[7030203739] 13[978703020373 1]

Press: Science Press

Publication date: 2007- 12- 1

Pricing: 26.00 yuan

abstract

System engineering is an important main course of management science and engineering specialty. This book is based on the idea of establishing a system, with the model method and its prediction function, evaluation function and simulation function as the main contents, with the logical process of quantitative model establishment, analysis and evaluation as the thinking route, and expounds the application of system engineering method with actual case systems. Through the study of this book, learners can master the basic concepts of systems engineering, master some commonly used analytical methods, and have the ability to apply the ideas, methods and technologies of systems engineering to solve practical social and economic problems.

This book is suitable as an undergraduate teaching material for management and economic majors, and can also be used as a reference book for system managers in social and economic industries.

System engineering is a comprehensive application technology and method of management science and engineering, which came into being and developed rapidly in the middle of the 20th century. This book is based on the idea of establishing a system, with the model method and its prediction function, evaluation function and simulation function as the main contents, with the logical process of quantitative model establishment, analysis and evaluation as the thinking route, and expounds the application of system engineering method with actual case systems. The purpose of this book is to provide more applicable teaching materials and reference books to improve the application efficiency and enhance the application effect of system engineering methods.

catalogue

order

1 chapter system and system engineering

The concept of 1. 1 system

1.2 concept of system engineering

Problems to be considered in this chapter

Chapter II System Modeling Method

2. The concept of1model

2.2 the method of establishing the model

2.3 System structure model

2.4 Analytic Hierarchy Process

Problems to be considered in this chapter