双量子阱能态结构研究

把共聚物简化为两个有限深量子阱———双量子阱模型 .着重研究了双量子阱中阱深、阱宽及势垒宽度对其能态结构的影响 ,从而对共聚物的合成等研究具有重要的指导意义 .

8羟基喹啉锌的能态结构研究

由于有机电致发光具有高亮度、低驱动电压、宽光谱范围(整个可见区)和丰富的材料选择等特点,在大面积平板显示器件研究中展现出广阔的应用前景.1987年Tang将多层结构引入有机电致发光器件以来,有机电致发光的研究在材料选择和器件结构等方面都取得了较大的进展.Adachi,等将有机电致发光器件制备成具有电子和空穴输运层的典型结构(ITO/空穴输运层/发光层/电子输运层/Mg:Ag).Burroughes和Heeger先后分别将聚合物引入有机电致发光研究中,用聚合物作为空穴输运层或发光层均取得了较好的效果.在有机小分子材料中,8羟基喹啉金属化合物一直是一个十分引人注目的材料体系,特别是8羟基喹啉铝和锌,其电致发光亮度超过15000cd/m^2.本文对8羟基喹啉锌的光致发光、吸收和激发光谱进行了研究,发现8羟基喹啉锌的发光来自380nm的吸收带,并且给出了可能的能态结构.1实验8羟基喹啉锌粉末材料是由本实验室自己合成的,其杂质浓度低于10^(-5).8羟基喹啉锌薄膜采用真空蒸发方法制备,蒸发时的真空度为1.07×10^(-2)Pa.8羟基喹啉锌粉末的光致发光光谱和激发光谱是利用MPF-4荧光分光光度计测量的,光致发光光谱的激发光波长为365nm,激发光谱的检测光波长为520nm.8羟基喹啉锌薄膜的吸收光谱是利用UV-360分光光度计测量的.

掺杂在GaAs材料中Be受主能级之间的跃迁

通过远红外吸收谱、光致发光光谱和拉曼散射光谱,对均匀掺杂在GaAs材料中Be受主能级之间的跃迁进行了研究.实验中使用的GaAs:Be样品是通过分子束外延设备,生长在半绝缘(100) GaAs衬底之上的外延单层.在4.2 K温度下,对样品分别进行了远红外吸收光谱、光致发光光谱、Raman光谱的实验测量.在远红外吸收光谱中,清楚地观察到了从Be受主1S3/2Γ8基态到它的三个激发态2P3/2Γ8, 2P5/2Γ8和2P5/2Γ7之间的奇宇称跃迁吸收峰.跃迁能量与先前文献中报道的符合得很好.从光致发光光谱中,观察到了Be受主从1S3/2Γ8基态到2S3/2Γ8激发态的两空穴跃迁的发光峰,从而间接地找到了两能级之间的跃迁能量.在Raman光谱中,清楚地分辨出来了Be受主从1S3/2Γ8基态到2S3/2Γ8激发态偶宇称跃迁的拉曼散射峰,直接得到了两能级间的跃迁能量.对比发现,分别直接和间接得到的1S3/2Γ8基态到2S3/2Γ8激发态跃迁能量结果是一致的.

Review of forest ecology studies in China

As the most important type or component in the terrestrial ecosystems, forest ecosystem makes its role obviously prominent and important on environment and human being. It possesses non-substitutable functions in the process of sustainable development. However, due to the complexity of the forest ecosystem and the relatively delay or lack of the related research technology, the science is still in the case of immature and questions. This paper summarized and reviewed briefly the development and the present case of the forest ecology, then pointed out the existing problems in the forest ecosystem researches. In the end, we discussed several fields that need to pay more attention to in future researches.

Bi-modal microstructure in a powder metallurgical ferritic steel

Ferritic steel with a nominal composition of Fe-14Cr-3W-0.42Ti-0.32Y was prepared by mixing gas-atomized prealloyed powder and mechanically alloyed powder. The microstructure is much different fxom other ferritic steels with the same composition and prepared via only mechanically alloyed powder. A bi-modal structure, which consists of pure ferritic grains and martensitic grains, was obtained after hot forging and air cooling. A phase transformation of αbcc→γfcc→α＇bcc was also discovered in microstructural observation. The bi-modal microstructure shows a good combination of high strength and high ductility.

Emergy Efficiency and Structural Adjustment of Hunan Agro-ecosystem

[Objective] To analyze the efficiency of Hunan agro-ecosystem in 1980- 2010. [Method] This paper adopts the emergy methods to evaluate the emergy input and output. [Result] The growth of total emergy input was mainly caused by the auxiliary factors in this phase. The proportion of the nonrenewable purchased emergy input to the total auxiliary emergy input increased from 21.80% in 1980 to 33.04% in 2010. In 1980-2010 the total emergy output of the system increased by 2.43 times, the proportions of the stock farming emergy output and fishery emergy output to the total emergy output increased sharply, while those of the planting emergy output and forestry emergy output showed a considerable decline. [Conclusion] The emergy yield ratio of this system was improved but its sustainability was worrying.

Microstructure and room temperature tensile property of as-cast Ti44Al6Nb1.0Cr2.0V alloy

The nominal Ti44Al6Nb1.0Cr2.0V alloy was newly designed and prepared by vacuum consumable melting technique with the ingot sizes of d225 mm×320 mm. The results show that the average lamella colony size is 780-1830 μm. This as-cast alloy has a modified near lamellar(M-NL) structure that is composed of mainly larger(α2+γ) lamella colonies and smaller(B2+equiaxed γ) blocky morphology. It exhibits the moderate tensile properties at room temperature, in which the Region(5) yields the ultimate tensile strength(UTS) about 499 MPa and the elongation about 0.53%. The obvious brittle fracture characteristics and trans-granular interlamellar fracture are the predominant modes. After room temperature tensile testing, there are some <101] and a few 1/2<112] superdislocations in the γ phase. The as-cast microcrack is the main factor to deteriorate the tensile property, which results in the premature fracture, poor ductility and few dislocations. The addition of Nb, Cr and V can decrease stacking fault energy(SFE) obviously, which is helpful to enhancing the ductility of the alloy.

Membrane-inspired quantum bee colony optimization and its applications for decision engine

In order to effectively solve combinatorial optimization problems,a membrane-inspired quantum bee colony optimization(MQBCO)is proposed for scientific computing and engineering applications.The proposed MQBCO algorithm applies the membrane computing theory to quantum bee colony optimization(QBCO),which is an effective discrete optimization algorithm.The global convergence performance of MQBCO is proved by Markov theory,and the validity of MQBCO is verified by testing the classical benchmark functions.Then the proposed MQBCO algorithm is used to solve decision engine problems of cognitive radio system.By hybridizing the QBCO and membrane computing theory,the quantum state and observation state of the quantum bees can be well evolved within the membrane structure.Simulation results for cognitive radio system show that the proposed decision engine method is superior to the traditional intelligent decision engine algorithms in terms of convergence,precision and stability.Simulation experiments under different communication scenarios illustrate that the balance between three objective functions and the adapted parameter configuration is consistent with the weights of three normalized objective functions.

An Improved Modal Strain Energy Method for Damage Detection in Offshore Platform Structures

The development of robust damage detection methods for offshore structures is crucial to prevent catastrophes caused by structural failures. In this research, we developed an Improved Modal Strain Energy （IMSE） method for detecting damage in offshore platform structures based on a traditional modal strain energy method （the Stubbs index method）. The most significant difference from the Stubbs index method was the application of modal frequencies. The goal was to improve the robustness of the traditional method. To demonstrate the effectiveness and practicality of the proposed IMSE method, both numerical and experimental studies were conducted for different damage scenarios using a jacket platform structure. The results demonstrated the effectiveness of the IMSE method in damage location when only limited, spatially incomplete, and noise-polluted modal data is available. Comparative studies showed that the IMSE index outperformed the Stubbs index and exhibited stronger robustness, confirming the superiority of the proposed approach.

Effects of secondary phases on texture and mechanical properties of as-extruded Mg-Zn-Er alloys

The effects of kinds of secondary phases on texture and mechanical properties of Mg-Zn-Er alloys were investigated. The results suggest that the I-phase has a great effect on modification of the texture via the discontinuous dynamic recrystallization mechanism（DDRX）, which tends to form well-developed equiaxed recrystallized grains. Meanwhile, the W-phase plays an important role in refining the grain size via continuous dynamic recrystallization（CDRX）, companied with a higher maximum texture intensity. Thus, the Mg-6Zn-1 Er alloy containing I-phase shows a performance of higher elongation of 20.4%. The Mg-2Zn-2Er alloy including W-phase displays a better tensile strength, and the yield strength（YS） is about 247 MPa.

Concept and Evaluation of Ecosystem Intrinsic Value

Ecosystem valuation can serve as a basis of scientific support for decision-making. So far, the most popular methods for ecosystem valuation are ecosystem service valuation （ESV）, which is based on the utility of ecosystem to human beings rather than on the objective value of the ecosystem. After more than 10 years＇ application, it has been found that all losses of ESV were about 10% of the benefits of human activities. In this paper, the ecosystem intrinsic value （EIV） is defined. EIV is an objective value that emerges from the existence, structures, functions and processes of ecosystem, but independent with man, man＇s will and preferences. The valuating approach and methods used for EIV were developed by using energy approach and the methods of emergy analysis and eco-exergy analysis. The EIV calculated by emergy from the substance, energy and information of ecosystem and by eco-exergy from the structure and function of ecosystem represents the existent value and the externally working capacity of ecosystem, respectively. The approach and methods of EIV evaluation were applied to Xiamen Bay, China. The results showed that the marine EIV in Xiamen Bay was 209 billion RMB, including 116 billion RMB of emergy and 92.4 billion RMB of eco-exergy in 2010, nearly 30 times of ESV and 8.5 times of the GDP of Xiamen marine industry in 2010. The EIV in unit area of Xiarnen Bay is more than 10 times higher than the average global ESV in estuaries. It implied a potential undervaluation to ecosystem value by ESV calculation, which may mislead decisions-making processes.

Effects of Mg content on microstructure and mechanical properties of SiC_p/Al-Mg composites fabricated by semi-solid stirring technique

10%(volume fraction) SiCp/Al-Mg composites with different Mg contents were successfully fabricated by semi-solid mechanical stirring technique under optimum processing conditions.Effects of Mg content on microstructure and mechanical properties were studied by scanning electron microscopy(SEM),X-ray diffractometry(XRD) and transmission electron microscopy(TEM).The results indicate that SiC particles disperse homogeneously in Al-Mg matrix and interfacial reaction between Al matrix and SiC particles is effectively controlled.Distribution of SiCp reinforcement and interfacial bonding are improved by adding Mg.Additionally,the mechanical properties of composites are remarkably improved with the Mg content increasing.

On modal energy in civil structural control

A new control strategy based on modal energy criterion is proposed to demonstrate the effectiveness of the control system in reducing structural earthquake responses. The modal control algorithm combining LQR(linear quadratic regulator) control algorithm is adopted in the discrete time-history analysis. The various modal energy forms are derived by definition of the generalized absolute displacement vector. A preliminary numerical study of the effectiveness of this control strategy is carried out on a 20-storey framed steel structural model. The controlled performance of the model is studied from the perspectives of both response and modal energy. Results show that the modal energy-based control strategy is very effective in reducing structural responses as well as in consuming a large amount of modal energy,while augmentation of additional generalized control force corresponding to the modes that contain little modal energy is unnecessary,as it does little help to improve the controlled structural performance.

Dynamic capabilities-based strategy innovation： a theoretical framework and empirical studies in Chinese firms

Based on investigations of 112 Chinese firms and studies on foreign leading corporations, a theoretical framework of dynamic capabilities based strategy innovation (SI) is put forward. Several large firms in China winning through SI were studied empirically. This paper complements previous publications on the theories of innovation and strategy. This work's findings will be useful for managers interested in our approach, which highlights the importance of SI and focuses on and points out the major pitfalls in the innovation processes. Implementing the dynamic capabilities based strategy innovation can effectively cultivate and develop core competences of corporations. It is concluded that implementing SI is the only path for Chinese enterprise growth in the intensified competition in the knowledge economy.

Effect of Post Spinning Modification on the PAN Precursors and Resulting Carbon Fibres

The impregnation of a special grade polyacrylonitrile （PAN） precursor fibres was carried out in a 8 wt. % KMnO4 aqueous solution to obtain modified PAN precursor fibres. The foctts is primarily on the effects of modification on the chemical structure and the physical mechanical properties of precursor ribres, them-aft stabilised and their resulting carbon fibres, which were characterized by the con-bination use of densities, wide-angle X-my diffraction （WAXD）, X-my photoelectron spectrosopy （XPS）, Elemental analysis （EA）, Fourier transform infrared （FT-IR） and scanning clectronmicroscope （SEM）, etc. KMnO4 as a strong oxidizer can swell, oxidize and corrode the skin of a precursor fibre, tin, form partly C≡N groups to C=N ones, decrcase the crystal size, increase the orientation index, increase the crystallinity index, furthermore increase the densities of modified PAN precursors and resulting thermal stabiliscd fibres. As a result, the carbonfibres developed from modified PAN fibres show an improvement in tensile strength of 31.25% and an improvement in elongation of 77.78%, but a decrease of 16.52% in Young＇s modulus.

Microstructure and dielectric properties of BaTi_4 O_9 (f)/0.64 BaTi_4 0_9+0.36 BaPr_2 Ti_4 O_(12) composites

The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti^(3+) and Ti^(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10^(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.

Structural Dynamics of 3-Dimethylamino-2-methyl-propenal in S2（ππ^＊） State

The photophysics of 3-dimethylamino-2-methyl-propenal （DMAMP） after excitation to the S2 （ππ^＊） electronic state was studied using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The transition barriers of the ground state tautomerization reactions between DMAMP and its three isomers were determined at B3LYP/6-311＋＋G（d,p） level of theory. The vibrational spectra were assigned. The A- band resonance Raman spectra were obtained in acetonitrile with excitation wavelengths in resonance with the first intense absorption band to probe the structural dynamics of DMAMP. The B3LYP-TD computation was carried out to determine the relative A-band resonance Raman intensities of the fundamental modes, and the result indicated that the vibronic-coupling existed in Franck-Condon region. Complete active space self-consistent field （CASSCF） calculations were carried out to determine the excitation energies of the lower-lying singlet and triplet excited states, the conical intersection points and the intersystem crossing points. The A-band short-time structural dynamics and the corresponding decay dynamics of DMAMP were obtained by analysis of the resonance Raman intensity pattern and CASSCF computations. It was found that a sudden de-conjugation between C1=O6 and C2=C3 occurred at the Franck-Condon region of the S2（ππ^＊） state, while the enhancement of the conjugation interaction between C3 and N（CH3）2, and between C1 and C2 evolutions shortly after the wavepacket leaves away the Pranck-Condon region via the excited state charge redistribution. The de-conjugation interaction between C1=O6 and C2=C3 made the rotation of C3=N（CH3）2 group around the C2-C3 bond much easier, while the enhanced conjugation between C1 and C2, and between C3 and N（CH3）2 made the rotation around the C1-C2 bond and C3-N5 more difficult. It was revealed that the initial structural dynamics of DMAMP was predominantly towards the CI-I（S2/S0） point, while the opportunities towards either CI-2（S2/S0） or CI-3（S2/S0） point were negligible. Two decay channels of DMAMP from S2,FC（ππ^＊） to So or Tl,min via various CIs and ISCs were proposed.

Microstructures and mechanical properties of Mg-10Ho-0.6Zr-xNd alloys

Mg-10Ho-0.6Zr-xNd (x=0, 1, 3 and 5, mass fraction, %) alloys were prepared by metal mould casting, and the microstructures and mechanical properties were investigated. The results show that the grain size of as-cast alloys reduces and the hardness and strength increase with the increase of Nd content. The alloys are aged followed by solid solution treatment. Mg-10Ho-0.6Zr-3Nd and Mg-10Ho-0.6Zr-5Nd alloys exhibit obvious age hardening response. The hardness value of Mg-10Ho-0.6Zr-5Nd alloy increases from HV104 at as-cast state to HV136 at peak-aged state. The maximum ultimate tensile strength and yield strength of the Mg-10Ho-0.6Zr-5Nd alloy are obtained in at peak-aged state, and the values are 323 MPa, 212 MPa at room temperature, and 258 MPa, 176 MPa at 250 ℃, respectively. The improvement of the tensile strength is mainly attributed to the fine and dispersively distributed plate-shaped β′ metastable phase.

Electronic and Optical Properties of Cubic SrHfO_3

In order to clarify the mechanism of optical transitions for cubic SrHfO_3, we have investigated the electronicstructure and optical properties of cubic SrHfO_3 using the plane-wave ultrasoft pseudopotential technique based on thefirst-principles density-functional theory (DFT).The ground-state properties, obtained by minimizing the total energy,are in favorable agreement with the previous work.From the band structure and charge densities as well as the theoryof crystal-field and molecular-orbital bonding, we have systematically studied how the optical transitions are affected bythe electronic structure and molecular orbitals.Our calculated complex dielectric function is in good agreement withthe experimental data and the optical transitions are in accord with the electronic structure.

Study on Life Prediction Model of Concrete Dam Based on Dry Zoning and Damage Theory

Concrete dam construction, reservoir impoundment and operation are a complicated and long-term process. During the course of this process dam suffers lots of factors including changing temperature, humidity, deformation, loads and restraints around dam. With time going by, damage to darn concrete happens. As a result, the strength, stiffness and resistance of concrete will decrease accompanying with damage accumulation and dam structure performance behavior and lifetime will be shorten or even destructed. At present, most of researches focus on concrete material itself and seldom consider effects of water content for concrete structures. That is apparently inconsistent with the actual situation. In engineering practice, it is urgently needed to assess existing dam structure damage state considering dry zoning in concrete. Through taking C30 dam concrete as standard specimen, alternate freezing and thawing tests are undertaken and changing law of time-dependent concrete damage state resulting in alternate wetting and drying has been studied in this paper. And then calculation formulas of time-dependent concrete damage evolution process considering alternate wetting and drying under condition of freeze-thaw cycle tests are established. Combining with four parameters Hsieh-Ting-Chen （ H -T-C ） model, some relevant factors or parameters are obtained through indoor testing and life prediction model of concrete dam based on dry zoning and damage theory is put forward which provides technical supports for dam safety evaluation and management of sustainable development.