航空复杂产品项目活动时间混合分布估算模型的改进

航空复杂产品开发项目具有复杂性、随机性、多目标性的特点,并且产品本身小批量、多品种的生产模式使得无法大量积累历史数据。因此,航空复杂产品项目活动时间存在高度的不确定性。如何能够更加合理、准确的描述其项目活动时间,对优化航空复杂产品的研制过程、缩短研制周期以及降低研制成本具有重大的意义。本文在Hahn基于PERT所建立的Beta Rectangular混合分布模型的基础上,保留其期望值的表达式,对其方差表达式进行改进。按照Malcolm、José等人的思想,将最可能值m与Beta分布的众数相对应,并且考虑其对方差的影响。仅保留PERT的一个假设,使方差的推导更多地依照于Beta分布而不是较多的近似。仿真结果表明,改进后的混合分布模型不但更具柔性,而且可以更加科学准确地描述航空复杂产品调度中高度不确定的任务持续时间状况。     

5.1-ps passively mode-locked Nd:Gd0.42Y0.58VO4 laser with a LT-GaAs absorber

We propose a diode end-pumped passively mode-locked Nd: Gd0.42 Y0.58 VO4 (Nd: GdYVO4) laser at 1064nm using a GaAs absorber grown at low temperature as the output coupler.Stable continuous-wave (CW) mode locking with a 5.1-ps pulse duration at a repetition rate of 113MHz is obtained.The maximum average output power is 2.29W at the incident pump power of 12W with the slope efficiency of about 24.8%.     

Raman Scattering at Resonant or Near-Resonant Conditions: A Generalized Short-Time Approximation

We investigate the dynamics of resonant Raman scattering in the course of the frequency de-tuning. The dephasing in the time domain makes the scattering fast when the photon energy is tuned from the absorption resonance. This makes frequency detuning to act as a cam-era shutter with a regulated scattering duration and provides a practical tool of controlling the scattering time in ordinary stationary measurements. The theory is applied to resonant Raman spectra of a couple of few-mode model systems and to trans-1,3,5-hexatriene and guanine-cytosine (G-C) Watson-Crick base pairs (DNA) molecules. Besides some particular physical effects, the regime of fast scattering leads to a simplification of the spectrum as well as to the scattering theory itself. Strong overtones appear in the Raman spectra when the photon frequency is tuned in the resonant region, while in the mode of fast scattering, the overtones are gradually quenched when the photon frequency is tuned more than one vibra-tional quantum below the first absorption resonance. The detuning from the resonant region thus leads to a strong purification of the Raman spectrum from the contamination by higher overtones and soft modes and purifies the spectrum also in terms of avoidance of dissociationand interfering fluorescence decay of the resonant state. This makes frequency detuning a very useful practical tool in the analysis of the resonant Raman spectra of complex systems and considerably improves the prospects for using the Raman effect for detection of foreign substances at ultra-low concentrations.     

Effects of the annealing duration of the ZnO buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process

In this study, the effects of the annealing duration of a zinc oxide (ZnO) buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process are discussed. A ZnO buffer layer was deposited on p-type Si (1 1 1) substrates by the metal organic chemical vapor deposition (MOCVD) method. After that, ZnO rods were grown on the ZnO-buffer/Si (1 1 1) substrate by a hydrothermal process. In order to determine the optimum annealing duration of the buffer layer for the growth of ZnO rods, durations ranging from 0.5 to 30 min were tried. The morphology and crystal structure of the ZnO/ZnO-buffer/Si (1 1 1) were measured by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The optical properties were investigated by photoluminescence (PL) measurement.     

爆破地震信号的分形盒维数值分析

在岩石场地进行了单段深孔爆破试验,获得了具有该场地特征的爆破地震波传播规律。从理论上推导了爆破地震波振动强度衰减系数K和与分形盒维数D以及盒维数计算中-lg(k) lgNk的双对数拟合直线方程参数b的关系。采用了适用于爆破地震波曲线双尺度特征的矩形盒模型计算了爆破地震波的盒维数D。数据分析表明:在同一场地条件下,爆破地震波的盒维数比较稳定,且爆破地震波振动强度的场地衰减指数与D为两倍的关系;药量和距离对盒维数拟合直线方程参数b的影响明显,且其关系与场地衰减指数对爆破地震波峰值强度的作用相近。通过数据分析,获得了参数b与爆破地震波振动峰值A的关系式:b=0.689lgA+3.0669,其相关系数为0.93。     

冰冻作用对固化污泥强度及变形特性影响

冻融作用会引起固化污泥的破坏,威胁工程体的稳定性。本文在封闭系统下,对固化污泥进行冻融试验,研究了不同冰冻发生时间及不同冻结时间对固化污泥抗压强度及变形特性的影响,并根据试验结果选取试样进行电镜扫描。研究结果表明:冻融作用对固化污泥的强度及变形特性影响很大,且源于冻融作用对固化污泥微观结构的影响;冰冻发生时间越早,水化程度越低,颗粒粘结越弱,固化体整体性越差,强度越低,冻融作用引起的强度衰减越大,固化体呈现塑性破坏;冰冻时间越长,引起的强度破坏越大,但强度衰减率随时间增加较小。上述研究成果可为寒区污泥固化填埋的安全处理提供技术参数及指导。     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

随机活动工期下求解资源约束项目最大期望净现值的动态调度算法

本文研究了随机活动工期下如何调度资源约束项目使得项目的期望净现值最大。首先对问题进行了界定,建立了相应的优化模型,其次针对问题的特点设计了一种动态规划算法。在算法设计的过程中,本文通过对项目网络图结构及不同状态最优值之间关系的分析,优化了动态规划算法状态的生成过程及状态最优值的求解过程,从而加快了算法的求解。使用随机生成的540个不同规模、不同结构的仿真案例对算法的有效性进行了验证,并分析了项目网络特征对算法效率的影响。实验发现：项目的次序强度对算法所需时间有着较大的影响,随着项目次序强度的减小,生成的状态数量会增加,从而计算时间也会增加。本文的研究可以为不确定环境下的项目调度提供决策支持。     

债券的防护型投资策略的随机过程分析

在文献［１］的基础上，对利率为随机过程情况，给出了期度的计算公式，并分析了此时债券的防护型投资策略     

基于债券久期的国债期货套期保值模型分析

使用久期的方法在中国国债期货市场上进行套期保值是否有效?使用久期的方法研究国债期货套期保值的效率问题在国外已经很多,然而这种方法是否适合于目前中国的国债市场,相关研究还不多见,还有待进一步的证实.为此借鉴国外相关理论,采用比较研究的方法,以国债期货上市后2013年9月到2014年5月初,国债现货和国债期货的数据为样本,以基于久期的最优套期保值比率模型为主,其他模型为辅,比较出最优套期保值效率.研究结果表明,基于久期的套期保值方法在目前中国的国债市场效果一般.