High Performance VHF Power VDMOSFETs for Low Voltage Applications

A high performance VHF power VDMOSFET,ap plying to the mobile communications,is developed,which can deliver an output power of 12W with the drain efficiency of 70% as well as the gain of 12dB at a low supply voltage of 12V and 175MHz.It is fabricated by using the terraced gat e structure and refractory molybdenum (Mo) gate technology.

The basic theory of industrial ecological economics

There is a great difference between the new type industrialization road in China and the road of industrialization first, then informatization and at last ecologization in western developed countries. Industrial eco-economics is one of the critical branches of eco-economics. It is a subject of objective law of structural upgrading, functional optimization and highly efficient running of industrial eco-economic system, which is combined with industrial economic system and eco-system under the condition of intellectual economy and circular economy combinations. Meanwhile, it is a relatively weak subject in the research field of eco-economics in China for the time being. Taking the practice road of new type industrialization needs the guidance of industrial eco-economics. The modern industrial eco-economics in the 21st century must be adapted to the need of new type road of industrialization in China. The paper analyzes the status quo of research and the main contents of industrial eco-economics and tries to study some key theories of the branch subject.

Electro-spark epitaxial deposition of NiCoCrAlYTa alloy on directionally solidified nickel-based superalloy

An 8 mm-high NiCoCrAlYTa coating was epitaxially built-up on a directionally solidified (DS) Ni-based superalloy blade tip by electro-spark deposition.Epitaxial morphologies of the coating and its microstructural characteristics were investigated by means of SEM,XRD and TEM etc.It is observed that the fine column-like dendrites originated from the γ'-particles or γ'-clusters of the DS substrate and are un-continuously coarsened.The β-phase particles precipitate and grow eutectically with the γ-phase.The orientation of fine column dendrites depends on electro-spark deposition processing parameters and the microstructure can be characterized with superfine γ and β phases.

Microstructure and phase forming process of Al-3Ti-0.2C-1RE grain refiner

An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.

Behaviors of Bellows-Like Origami Patterned Tubes with Trapezoidal Patterns

In this paper, we show one of the possibility utilizing typical origami structures for civil engineering fields such as the bridge bearing support. We numerically investigate axial spring constants and buckling behaviors of bellows-like origami tube structures. The bellows-like origami tube structures, which can be folded because of elastic deformations, work as a kind of spring. If the initial heights of the bellows-like origami tubes are less than 90% of the height of the prismatic tubes without bellows-like folded lines, the spring constants of the bellows-like tubes are very low compared with those of the prismatic tubes. The buckling loads and patterns of the bellows-like tubes vary depending on the initial heights of the tubes.

Influence of concrete differential aging time on the construction phases analysis of the Fenghua River Bridge

The Fenghua River Bridge is a major structure on the highway between Hengzhang and Guojiachi, which is to be built with a four-span prestress concrete (PC) box girder and symmetrical cantilever castings. In this paper, a finite element method (FEM) model is set up to study the effects of concrete differential aging time on the construction phases of the Fenghua River Bridge by calculating the vertical displacement of the folding segment of the middle span and the longitudinal bending moment of Pier 12#. In the model, the girders are classified into 150 changing sections based on the desgn scheme, and their construction is to be carried in 16 phases respectively to build 12 blocks connected by a side folding segment and a middle folding segment, covered with a second dead load and in completion for 20 years. It is found that the internal forces and deformations of the concrete structures at the aging time of 60 d are quite different from those of 0 d aging time while the behaviors of the structures of 120 d aging time is nearly the same as those of 60 d aging time― the differences are so small that can be neglected, suggesting that the creep develops obviously about one month after the cement is hardened and the development fades later on.

复合材料工型长桁热隔膜成型工艺

采用自动铺带设备和热隔膜成型设备制备了碳纤维复合材料工型长桁预制体。分析成型温度、成型速率、成型压力对工型长桁预制体的表观质量、厚度的影响。结果表明,制备工型长桁预制体厚度均匀性受温度变化影响较小,但会随着成型速率的降低而减小。当成型温度较低时,层间滑移能力差,每层预浸料的变形量不一致,造成R角位置容易出现纤维褶皱;当成型温度较高时,预成型体内夹杂空气容易排除。预制体的厚度分布均匀性主要受成型速率和成型压力的影响。试验采用的方案,工型长桁预制体R角处的厚度均小于缘条和腹板的厚度。

Progress in study on constructal theory and its applications

The emergence and development of constructal theory,which has been a new discipline branch to research sorts of structures in nature and engineering,are reviewed.The core of the constructal theory is that various shapes and structures of the matters in nature are generated from the tendency to obtain optimal performance.Constructal theory and its application are summarized,from disciplines such as heat,mechanism,fluid flow,electricity,magnetism and chemistry,to life and non-life systems in nature.

Process structuring of polymers by solid phase orientation processing

Solid phase orientation of polymers is one of the most successful routes to enhancement of polymer properties.It unlocks the potential of molecular orientation for the achievement of a range of enhanced physical properties.We provide here an overview of techniques developed in our laboratories for structuring polymers by solid phase orientation processing routes,with a particular focus on die drawing,which have allowed control of significant enhancements of a single property or combinations of properties,including Young's modulus,strength,and density.These have led to notable commercial exploitations,and examples of load bearing low density materials and shape memory materials are discussed.

An ultrahigh strength steel produced through deformation-induced ferrite transformation and Q&P process

In this work,DIFT technology and Q&P process were combined in order to introduce ultrafine-grained ferrite into the matrix of martensite and retained austenite to develop a new kind of advanced high strength steel,and two kinds of steels were investigated by this novel combined process.The newly designed process resulted in a sophisticated microstructure of a large amount of ferrite(about 5 m in diameter),martensite and a considerable amount of retained austenite for TRIP 780 steel.The ultimate tensile strength can reach about 1200 MPa with elongation above 16% for TRIP 780,that is much higher than the one solely treated by Q&P process.Tensile tests showed that both steels with the novel combined process achieved a good combination of strength and ductility,indicating that the new process is promising for the new generation of advanced high strength steels.