一种基于分数阶Fourier变换的雷达运动目标检测算法

针对雷达回波为多分量LFM信号时,时频分析存在的交叉项干扰问题,提出了一种基于分数阶Fourier变换(Fractional Fourier Transform,FRFT)的伪Wigner分布(PWD).该方法通过在参数平面按阈值进行峰值搜索确定变换域阶次,再在相应的分数阶Fourier域计算PWD,有效地抑制了交叉项的干扰,有利于更好地提取信号的时频信息.仿真实验证明了在强背景噪声下该算法的有效性.     

随钻地层压力测量模拟实验研究

与传统技术相比,随钻地层压力测试工具测量的地层压力数据能更好地反映地层的真实压力状况,据此可优化钻井工艺、提高钻井效率。根据地层压力数据确定的压力梯度和流体界面等信息进行井眼导向,实时调整钻井液密度,及时识别和发现一些复杂的钻井地质环境因素。文章从FRA理论分析入手,利用地面模拟实验平台(地层液体抽汲组合测量装置)对4块不同尺寸、不同孔隙度和渗透率的砂岩岩心进行模拟地层液体抽汲实验,通过解释程序得出4块岩心的压力—时间关系图并预测地层压力。     

Study of Binqui. An application for smartphones based on the problems without data methodology to reduce stress levels and improve academic performance of chemical engineering students

Chemical Engineering students are usually exposed to stress and anxiety situations during university period. Authors consider that a reduction in students’ stress levels can improve their academic results. A new experience based on the introduction of gamification strategies by incorporating a new methodology for solving engineering problems called PWD (problems without data) was proposed. This was related with a specific app design. Two students’ groups were randomly done and, despite having the same academic content and teacher, only one group used this methodology. Results showed that using these new elements for a subject called Basic Operations, belonging to the area of Chemical Engineering area of the University of León, the comfort and stress level of the students improved significantly. Thus, the average value of the stress perceived by the students, which initially was above a value of 5 out of 10, was reduced for those students who have followed the proposed methodology to levels below 3.5. Additionally, an related to the academic degree, a difference of 1.5 points (out of 7) was found for the students who had used the PWD methodology with respect to the control students.     

Investigation of the benefits of plasma deposition for the additive layer manufacture of Ti-6Al-4V

With increasing emphasis on sustainability, additive layer manufacturing (ALM) offers significant advantages in terms of reduced buy-to-fly ratios and improved design flexibility. Plasma wire deposition is a novel ALM technique in which plasma welding and wire feeding are combined. In the present work, a working envelope for the process using Ti-6Al-4V was developed, and regression models were calculated for total wall width, effective wall width and layer height. The plasma wire deposition process is able to produce straight walls of widths up to 17.4 mm giving a maximum effective wall width after machining of 15.9 mm, which is considerably wider than competing processes. In addition, for Ti-6Al-4V the deposition efficiency averages 93% and the maximum deposition rate is 1.8 kg/h. Coarse columnar grains of β phase grew from the base during deposition, which transformed into a Widmanstätten structure of α lamellae on cooling. Bands were identified in the deposits, which had a repetitive basket-weave microstructure that varied in size. The strength measured by micro-indentation hardness of 387 HV on average is as much as 12% higher than the substrate. These preliminary results indicate that plasma wire deposition is likely to be a suitable process for the ALM of large aerospace components.     

深水钻井早期井涌检测方法及其未来趋势

深水钻井技术是制约深海油气勘探开发的主要因素之一。深水钻井具有高风险,高投资,高回报等特点,深水井控是深水钻井的一个难点,如何有效地预测发现井涌是深水井控的关键。分析了各种常用的井涌检测方法并结合深水钻井的特殊工况,指出常用的井涌检测方法无法满足深水井控的要求,最后介绍了一种使用LWD、PWD监测井涌的井涌早期监测方法,使用PWD实时监测井底的压力变化情况,并对水力模型进行修正,同时建立井底压力正常趋势线;使用LWD实时测量地层参数,利用浅侧向电阻率随钻测量等工具监测钻井液性能变化,可以有效地实现流体侵入早期监测。     

A case study into the language structure of construction standard form in Malaysia

Different interpretation could denote a dispute regarding the contractual obligations and expectation between the contracting parties. This paper addresses the need for clarity of standard form in Malaysia. Hence the objectives are to identify the problems in the language structure of standard form from the viewpoint of professionals, and the measures for improving the language structure of standard form. The research aims to mitigate or prevent construction disputes through better interpretation and understanding of construction contracts, and it offers a proactive approach to avoid the inevitability of conflicts occurring in a project. The data collection was mainly by questionnaire survey. Two experts from construction contracting were appointed to approve the questionnaire design and verify the research outcomes. The results identified eight clarity aspects and three legalese problems of language structure in PWD 203A (Rev. 10/83) Form. Besides, twelve out of thirteen measures were agreed upon by the respondents as to ways for improving the language structure. It is concluded that clarity needs to be considered in future contract drafting towards the understanding of standard forms, and thereby to contribute to the avoidance of disputes.     

具有脉冲宽度优化的1.25Gb/s激光驱动器

A 1.25 Gb/s laser diode driver (LDD) with pulse width optimization has been implemented in a 0.6-μ m BiCMOS process. This paper illustrates the relation between the pulse width distortion (PWD) of the output eye diagram and the driving amplitude from the second pre-amplifier. Also, a specific current setting circuit working together with an LDD is proposed to generate the optimum driving amplitude and to avoid device nonlinearity, temperature variation and process deviation. The measured results show a maximum crossing deviation of –3% and indicate the desired independence and stability.     

A 1.25 Gb/s laser diode driver with pulse width optimization

A 1.25 Gb/s laser diode driver(LDD) with pulse width optimization has been implemented in a 0.6-μm BiCMOS process.This paper illustrates the relation between the pulse width distortion(PWD) of the output eye diagram and the driving amplitude from the second pre-amplifier.Also,a specific current setting circuit working together with an LDD is proposed to generate the optimum driving amplitude and to avoid device nonlinearity,temperature variation and process deviation.The measured results show a maximum c...     

Research on Feature Extraction of Composite Pseudocode Phase Modulation-Carrier Frequency Modulation Signal Based on PWD Transform

The identification features of composite pseudocode phase modulation and carry frequency modulation signal include pseudocode and modulation frequency. In this paper, PWD is used to extract these features. First, the feature of pseudocode is extracted using the amplitude output of PWD and the correlation filter technology. Then the feature of frequency modulation is extracted by way of PWD analysis on the signal processed by anti-phase operation according to the extracted feature of pseudo code, i.e. position information of changed abruptly point of phase. The simulation result shows that both the features of frequency modulation and phase change position caused by the pseudocode phase modula- tion can be extracted effectively for SNR = 3 dB.     

Wigner-Ville分布及其在故障诊断中的应用

机械系统故障信号通常都是非平稳的,联合时频分布是对故障信号分析的重要且有力的工具,Wigner-Ville分布可从时域特征与频域特征的结合途径揭示非平稳信号的构成本质。文章简单介绍了Wigner-Ville分布的物理意义及其主要性质,并通过实验探讨了用Wigner-Ville分布处理诊断信号的优点。