a requirement traceability refinement method based on relevance feedback

Knowledge Systems Institute Graduate School

基于相关反馈的需求跟踪关系建立和维护方法

需求跟踪是一种描述和跟踪整个需求生命周期的手段和方法，它是需求工程的重要组成部分。一个全面的需求跟踪关系能够辅助软件开发生命周期中很多活动的执行，并为决策分析和权衡提供依据。传统手工建立和维护需求跟踪关系的方法，在实际应用中面临着成本过高、容易出错、难以维护等问题。 为了帮助克服手工建立、维护需求跟踪关系的这些缺点，研究者提出了动态需求跟踪方法。动态需求跟踪使用信息检索、自然语言处理等技术，自动化地建立需求和工作产品之间的跟踪关系，提高了需求跟踪的效率。然而已有的方法依然需要进一步完善，其中比较突出的有两个方面：一是需求跟踪关系建立的精度有待提高，二是需求跟踪关系维护的自动化程度有待增强。这两个问题制约着动态需求跟踪方法在实际软件开发过程中的应用。如果动态需求跟踪不能保证足够的精度，建立的结果对于需求跟踪的辅助作用就会大打折扣，也就会降低方法在实际使用的价值。同时，需求跟踪关系的建立并非一劳永逸，需求和工作产品随着开发过程的进行而不断变化，这就导致跟踪关系需要不断地更新和维护。自动化、半自动化的维护跟踪关系将会促进动态需求跟踪方法在实际项目中的使用。 本文研究了现有的动态跟踪技术，重点探讨了基于信息检索技术的动态需求跟踪方法。基于以上分析，本文使用相关反馈技术改善动态需求跟踪在需求跟踪关系建立和维护中面临的问题。在跟踪关系建立上，提出了一种基于相关反馈的需求跟踪关系建立方法MERTRF（A Method for Establishing Requirement Traceability based on Relevance Feedback）。该方法使用信息检索技术建立需求跟踪关系，并使用相关反馈提高跟踪建立的精度。在跟踪关系维护上，提出了一种针对工作产品变更的跟踪关系维护方法MMRTRF（A Method for Maintaining Requirement Traceability based on Relevance Feedback from work product changes）。该方法针对工作产品的不同变更类型采用不同的维护方法自动更新跟踪关系，并使用相关反馈技术提高维护的精度和效率。同时，本文实现了提出的方法，完成了一个动态需求跟踪管理工具DRTMTool（Dynamic Requirement Traceability Management Tool）。该工具使用信息检索技术来实现跟踪关系的建立，使用向量空间模型等信息检索模型计算需求文档和工作产品之间的相似度，通过自动翻译解决中文文本和英文代码之间的匹配问题。最后本文通过使用实际的项目数据进行实验，验证了动态跟踪工具的效果。

First-passage failure and its feedback minimization of quasi-partially integrable Hamiltonian systems

An n degree-of-freedom Hamiltonian system with r (1¡r¡n) independent 0rst integrals which are in involution is calledpartially integrable Hamiltonian system. A partially integrable Hamiltonian system subject to light dampings andweak stochastic excitations is called quasi-partially integrable Hamiltonian system. In the present paper, the procedures for studying the 0rst-passage failure and its feedback minimization of quasi-partially integrable Hamiltonian systems are proposed. First, the stochastic averaging methodfor quasi-partially integrable Hamiltonian systems is brie4y reviewed. Then, basedon the averagedIt ˆo equations, a backwardKolmogorov equation governing the conditional reliability function, a set of generalized Pontryagin equations governing the conditional moments of 0rst-passage time and their boundary and initial conditions are established. After that, the dynamical programming equations and their associated boundary and 0nal time conditions for the control problems of maximization of reliability andof maximization of mean 0rst-passage time are formulated. The relationship between the backwardKolmogorov equation andthe dynamical programming equation for reliability maximization, andthat between the Pontryagin equation andthe dynamical programming equation for maximization of mean 0rst-passage time are discussed. Finally, an example is worked out to illustrate the proposed procedures and the e9ectiveness of feedback control in reducing 0rst-passage failure.

Optimal feedback control of two-photon fluorescence based on genetic algorithm

An optimal feedback control of two-photon fluorescence in the ethanol solution of 4-dicyanomethylene-2-methyl-6-p-dimethyl-amiiiostryryl-4H-pyran (DCM) using pulse-shaping technique based on genetic algorithm is demonstrated experimentally. The two-photon fluorescence of the DCM ethanol solution is enhanced in intensity of about 23%. The second harmonic generation frequency-resolved optical gating (SHG-FROG) trace indicates that the effective population transfer arises from the positively chirped pulse. The experimental results appear the potential applications of coherent control to the complicated molecular system.

Optimal feedback control of two-photon fluorescence in Coumarin 515 based on genetic algorithm

An optimal feedback control of two-photon fluorescence in the Coumarin 515 ethanol solution excited by shaping femtosecond laser pulses based on genetic algorithm is demonstrated experimentally. The two-photon fluorescence intensity can be enhanced by similar to 20%. Second harmonic generation frequency-resolved optical gating traces indicate that the optimal laser pulses are positive chirp, which are in favor of the effective population transfer of two-photon transitions. The dependence of the two-photon fluorescence signal on the laser pulse chirp is investigated to validate the theoretical model for the effective population transfer of two-photon transitions. The experimental results appear the potential applications in nonlinear spectroscopy and molecular physics. (c) 2005 Elsevier B.V. All rights reserved.

Stimulated Raman adiabatic passage from atomic to molecular Bose-Einstein condensates: Feedback laser-detuning control and suppression of dynamical instability

We present a feedback control scheme that designs time-dependent laser-detuning frequency to suppress possible dynamical instability in coupled free-quasibound-bound atom-molecule condensate systems. The proposed adaptive frequency chirp with feedback is shown to be highly robust and very efficient in the passage from an atomic to a stable molecular Bose-Einstein condensate.

Theoretical model for a periodically driven semiconductor laser subject to optical feedback from a microcantilever

We propose a theoretical model for analyzing the dynamics of a periodically driven semiconductor laser subject to optical feedback from a microcantilever. We numerically investigate the temporal evolution of the light intensity of the semiconductor laser, and we show the interspikes of the light intensity. These interspikes of light intensity are also demonstrated in our experiment. The validity of the theoretical model is verified. The observed phenomenon has a potential application for resonant sensing. (C) 2008 Optical Society of America.

Instabilities in a grating feedback external cavity semiconductor laser

Output power fluctuations in a grating external cavity diode laser with Littman configuration are described, showing peculiar chaotic behaviors of self-pulsation at the L-I curve kink points. Different spectral characteristics with multiple peaks are observed at upper and lower state of the self-pulsation. It is found also that P-N junction voltage jumps in a same pace with the pulsation. The observed phenomena reflect competition between different longitudinal modes, and transient variation of transverse modes in addition. These experimental results may contain information about the mechanisms of the chaotic instability in strong filtered feedback semiconductor lasers. (C) 2008 Optical Society of America

Stabilization of optical Fabry-Perot sensor by active feedback control of diode laser

This paper presents the design and characterization of a fiber Fabry-Perot interferometer (FFPI) acoustic wave detector with its Q point being stabilized actively. The relationship between the reflectivity of the F-P cavity facets and cavity length was theoretically analyzed, and high visibility of 100% was realized by optimized design of the F-P cavity. To prevent the drifting of the Q point, a new stabilization method by actively feedback controlling of the diode laser is proposed and demonstrated, indicating the method is simple and easy operating. Measurement shows that good tracing of Q point was effectively realized. (c) 2008 Elsevier B.V. All rights reserved.

Single mode Er-doped pi-phase-shifted distributed feedback fibre grating laser

A novel method incorporating the shielded method and the post-processing method has been proposed to fabricate the pi-phase-shilted fibre grating. Then an Er-doped pi-phase-shifted distributed feedback fibre grating laser has been fabricated using the grating. The laser threshold is 20 mW. When pumped with 90 mW light at 980 nm, the laser gives an output of 1.1 mW. Its signal-to-noise ratio is better than 60 dB. It is demonstrated that the laser is single mode operation by means of a Fabry-Perot scanning interferometer.

Theoretical modelling of the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers

By employing a simple model of describing three-level lasers, we have theoretically investigated the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers. And based on the theoretical analysis we have proposed a promising method to suppress self-pulsing behaviour in the fibre lasers.

Optical properties of zirconia-titania-ORMOSIL films for temperature tuning distributed feedback waveguide lasers

The zirconia-titania-ORMOSIL waveguide thin films with considerable optical quality were prepared by the sol-gel process. The refractive index (n) and the extinction coefficient (k) were determined by a scanning ellipsometer. Wavelength tunable output of distributed feedback waveguide lasing was demonstrated in Rhodamine 6G doped ZrO2 TiO2-ORMOSIL thin films by varying the temperature, and about 5.5 nm wavelength tuning range was achieved around the emission wavelength of 599 nm. The thermal-optic coefficient (dn/dT) of the active ZrO2-TiO2-ORMOSIL films was deduced. (c) 2005 Elsevier B.V. All rights reserved.

Line-width reduction of a laser diode array using an external cavity with two feedback mirrors

A novel Littman-Metcalf external cavity laser diode array with two feedback mirrors is introduced. The line-width broadening effect caused by smile can be reduced by the novel external cavity. At the drive current of 16A, the line-width is narrowed to 0.1nm from free-running width of 1.6nm with output efficiency of 84%.