变高箱梁上跨多股既有铁路支承体系施工方法研究

结合柳州东外环柳东段上跨湘桂铁路单箱四室变高结构预应力砼连续箱梁施工实例,本文详细阐述了采用螺旋钢管立柱贝雷梁支架结合碗扣式满堂支架做为承重体系的设计、结构承载验算及支承体系施工关键技术。

深井大地压泵房围岩变形破坏特性研究

以峰峰集团有限公司万年矿-440泵房为例,对深井大地压泵房围岩在复杂应力条件下围岩变形及其特征进行了现场观测及分析研究。结果表明在复杂应力条件下深井大地压围岩具有明显的流变特性,其变形表现为全断面不规则变形,底鼓是导致围岩破坏的主要原因。

Novel forward mode AC/AC converters with high frequency link

A circuit configuration and a circuit topologic family of the novel forward mode AC/AC converters with high frequency link are presented. The circuit configuration is constituted of input cycloconverter, high frequency transformer, output cycloconverter, input and output filters. The circuit topologic family includes eight circuit topologies, such as full-bridge-full-wave mode, etc. The bi-polarity phase-shifted control strategy and steady principles are thoroughly investigated. The output characteristics are obtained. By using the bi-polarity phase-shifted control strategy with phase-shifted control between the output cycloconveter and the input cycloconverter, commutation overlap period of the output cycloconverter, and polarity selection of the output filtering inductance current and the input voltage, the leakage inductance energy and the output filtering inductance current are naturally commutated, and surge voltage and surge current of the cycloconverters are overcome. The converters have such advantages as simple topology, two-stage power conversions(LFAC/HFAC/LFAC), bi-directional power flow, high frequency electrical isolation, good output waveforms, and strong ability to stabilize voltage. The converters lay key technical foundation on a new-type of regulated sinusoidal AC power supplies and electronic transformers. The correction and advancement of the converters are well verified by a principle test.

THE RESEARCH OF RHEOLOGICAL PROPERTIES OF STOWING SLURRY WITH HIGH-WATER MATERIALSOLIDIFYING TAILINGS

High-water material, tailings from goldmine and water are mixed into a new slurry.Testing of rheological properties of stowing slurries A and B is made to determine type and rheological parameters of the slurry. The main factors influencing rheological properties of the slurry are analyzed and the rational concentration and empirical resistance calculating formula of pipe line transportation are presented.

Structure of different types of coal metamorphism by HTEM

In order to discuss the effect of tectonic stress on the structural evolution of coal, given the importance attached to High-resolution Transmission Electron Microscopy (HTEM), we investigated several aspects of material structures of high-rank Carboniferous period coal, located in the northern foreland basin of the Dabie orogenic belt in eastern China. High powered crystal lattice images of Bright Fields (BF) and Selected Area Diffraction patterns (SAD) of different types of metamorphism in coal were obtained. The results show that the Basic Structural Units (BSU) become increasingly more compact as a function of rising tem-perature and pressure. Under pressure, the local orientation of molecules is strengthened, the arrangement of BSU speeds up and the degree of order is clearly enhanced.

Power Transfer of PV Inverter from DC to AC Voltage Source

This paper presents a simple approach of a topology already known in the literature, applied in active power transfer from direct current source to any alternating current voltage source, whether the utility power or a voltage inverter that is forming an isolated AC grid. The photovoltaic inverter works as current controlled voltage source inverter that provides a sinusoidal current to the AC grid. The inverter is insulated from the grid by a transformer. The system is discussed and modeled. Simulation results of this application are presented and experimental results validate this topology.

High Frequency Transformers for DC/DC Converter Used in Solar PV System

This paper presents and investigates planar and coaxial high frequency power transformers used for DC/DC converters in a three phase photo voltaic （PV） power systems. The winding structure including a Faraday shield between the primary and secondary windings is designed to minimize eddy current losses, skin and proximity effects, and to reduce the leakage inductance, and the inter winding coupling capacitance. Finite Element Method is employed to analyze the magnetic flux and eddy current distributions. The two different kinds of prototype high frequency transformers are designed and tested. The simulation and experiment results are demonstrated and compared with non-shielded transformers. The shielded transformers have achieved the expected results with a relatively small coupling capacitance, compared with the conventional high frequency transformer. This shield decreases the inter-winding coupling capacitance Cps. The topology of this shield has to be such that it acts as a Faraday screen while avoiding eddy current generation.

High-Strain Fiber Bragg Gratings for Structural Fatigue Testing of Military Aircraft

This paper reports on an experimental program of work which investigates the reliability, durability, and packaging of fiber Bragg gratings （FBGs） for application as distributed strain sensors during structural fatigue testing of military platforms. The influence of the FBG fabrication process on sensor reliability is investigated. In addition, methodologies for broad-area packaging and surface-mounting of FBG sensing arrays to defense platforms are developed and tested.

Improved multilevel storage capacity in Ge_(2)Sb_(2)Te_(5)-based phase-change memory using a high-aspect-ratio lateral structure

Further improvement of storage density is a key challenge for the application of phase-change memory(PCM)in storage-class memory.However,for PCM,storage density improvements include feature size scaling down and multilevel cell(MLC)operation,potentially causing thermal crosstalk issues and phase separation issues,respectively.To address these challenges,we propose a high-aspect-ratio(25:1)lateral nanowire(NW)PCM device with conventional chalcogenide Ge_(2)Sb_(2)Te_(5)(GST-225)to realize stable MLC operations,i.e.,low intra-and inter-cell variability and low resistance drift(coefficient=0.009).The improved MLC performance is attributed to the high aspect ratio,which enables precise control of the amorphous region because of sidewall confinement,as confirmed by transmission electron microscopy analysis.In summary,the NW devices provide guidance for the design of future high-aspect-ratio threedimensional PCM devices with MLC capability.

High performance steels:Initiative and practice

In order to meet the progressive requirement for the performance improvement of steel,the author proposed a novel microstructure featured with multi-phase,meta-stable and multi-scale(so-called as M 3).And then,the new technologies could be developed to process three prototype steels with high performance:the third generation high strength low alloy(HSLA) steels with improved toughness and/or ductility(AKV(40℃)≥200 J and/or A≥20% when Rp0.2 in 800-1000 MPa),the third generation advanced high strength steels(AHSS)(Rm×A≥30 GPa% when Rm from 1000 MPa to 1500 MPa) for automobiles with improved ductility and low cost,and heat resistant martensitic steels with improved creep strength(10000650≥90 MPa).It can be expected that the new technology developed will remarkably improve the safety and reliability of steel products in service for infrastructures,automobiles and fossil power station in the future.

Eggshell-inspired membrane—shell strategy for simultaneously improving the sensitivity and detection range of strain sensors

The tradeoff between sensitivity and detection range(maximum and minimum stretchability)is a key limitation in strain sensors;to resolve this,we develop an efficient and novel strategy herein to fabricate a highly sensitive and stretchable strain sensor inspired by the membrane-shell structure of poultry eggs.The developed sensor comprises a soft and stretchable surface-grafting polypyrrole(s-PPy)film(acting as the membrane)and a brittle Au film(acting as the shell),wherein both films complement each other at the electrical and mechanical levels.Au forms cracks under strain contributing to its high sensitivity and low detection limit,and s-PPy can bridge Au cracks and increase stretchability which has not been used in strain sensors before.The surface-grafting strategy not only enhances interface adhesion but also tunes the brittle property of native PPy to render it stretchable.Utilizing the synergetic effect of the membrane-shell complementary structure,the strain sensors achieve ultrahigh sensitivity(>10^(7)),large stretchability(100%),and an ultralow detection limit(0.1%),demonstrating significant progress in the field of strain sensors.The membrane-shell(Au/s-PPy)-structured strain sensor can successfully detect finger motion,wrist rotation,airflow fluctuation,and voice vibration;these movements produce strain in the range of subtle to marked deformations.Results evidence the ultrahigh performance and bright application prospects of the developed strain sensors.

Ausforming effects on anisotropy of mechanical properties in HSLA martensitic steel

In order to clarify effects of prior pancaked austenitic structure on microstructure and mechanical properties of transformed martensite in ausformed steel,a super-thin pancaked austenite was processed by multi-pass rolling in a 0.03-2.6Mn0.06Nb-0.01Ti(wt%) low alloy steel.The evolution of prior pancaked austenite grain during multi-pass rolling was studied using Ni-30Fe model alloy.Related with the structure and texture in the prior super-thin pancaked austenite in Ni-30Fe alloy,the texture and anisotropy of mechanical properties of transformed martensite in the studied ausformed steel were focused on.There were mainly three kinds of rolling texture components in the super-thin pancaked austenite:Goss {110} 001,copper {112} 111 and brass {110} 112.They were further transformed into the weak {001} 110 and strong {112} 110,{111} 112 texture components in the martensitic structure.The orientation relationship(OR) of lath martensite transformation from pancaked austenite in the ausformed steel deviated larger from the exact Kurdjumov-Sachs(K-S) OR than in the case of equiaxed austenite without deformation.The tensile and yield strengths of the ausformed martensitic steel first decreased and then increased as the angle between tension direction and rolling direction increased.The main reason for the anisotropy of strength was considered as the texture component {112} 110 in martensite.However,the anisotropy of impact toughness was more complex and the main reasons for it are unknown.

E-beam-induced in situ structural transformation in one-dimensional nanomaterials

Electron beam （e-beam） irradiation is an inev- itable, but crucial issue for electron microscopy. Our investigation results show the e-beam-induced in situ structural transformations in silicon （Si） nanowires and zinc oxide （ZnO） nanowires （NWs）, respectively. Crystal to amorphous structure transition was revealed in Si NWs utilizing high resolution electron microscopy and electron energy loss spectroscopy. Reconstruction at the （1010） surface of ZnO NWs was also observed in the transmission electron microscope （TEM） using aberration-corrected electron microscopy. These e-beam-induced in situ struc- tural transformations prove that the electron beam irradi- ation effect is able to be used for the local modification of one-dimensional nanomaterials.

Generalized Population Aging in China: A National-Level Analysis Based on Provincial Simulations

The age structure of the Chinese population is entering a process of generalized aging in which the major age groupings will see a fall in the ratio of younger age groups and a rise in the ratio of older age groups,with varying levels of socioeconomic significance for the entire population system.The implementation of the unconditional two-child policy(quanmian erhai zhengce)has not changed this general trend.The early stage of population aging(2011-2060)is one of the high-speed development of generalized aging with multiple growth peaks and fluctuations in the size,growth rate and internal structure of the major age groupings.From the perspective of generalized population aging,China’s future contains four major systemic demographic dividends and faces four major systemic demographic risks.The early stage of aging is the most important period for the transformation of the population age structure.If society can adjust to the aging trend and the phased nature of the development of this trend,it will be able to seize the initiative in long-term development.

Phase Transition and Physical Properties of InS

Using the crystal structure prediction method based on particle swarm optimization algorithm, three phases （Pnnm, C2/m and Pm-3m） for InS are predicted. The new phase Pm-3m of InS under high pressure is firstly reported in the work. The structural features and electronic structure under high pressure of InS are fully investigated. We predicted the stable ground-state structure of InS was the Pnnm phase and phase transformation of InS from Pnnm phase to Pm-3m phase is firstly found at the pressure of about 29.5 GPa. According to the calculated enthalpies of InS with four structures in the pressure range from 20 GPa to 45 GPa, we find the C2/m phase is a metastable phase. The calculated band gap value of about 2.08 eV for fnS with Pnnm structure at 0 GPa agrees well with the experimental value. Moreover, the electronic structure suggests that the C2/m and Pm-3m phase are metallic phases.