子流域划分对HSPF模型径流模拟效果的影响

在水文水质模拟过程中,子流域划分数量直接影响模拟结果的精确度,确定最佳子流域划分方案对提高模拟精确度至关重要。基于PEST-HSPF模型,以中河流域为例,在相同参数及不同参数条件下,采用PEST自动校准方法,判断子流域划分数量对流量模拟精确度的影响。结果表明,在相同水文参数下,子流域划分数量变化时,模拟流量的纳什系数(NSE)和可决系数(R2)在0.65~0.78之间波动,其中子流域划分数量在10~20之间对模拟结果的精确度影响最大;在不同水文参数下,径流模拟结果的NSE与R2随子流域划分数量的增加先增大后减小,相对误差(RE)在子流域划分数量介于1~10之间时急剧下降后趋于稳定;子流域划分对HSPF水文模拟效果影响显著,表现出阈值效应,当划分数量超出阈值范围时,径流模拟精度均会受到很大影响。     

Effect of obstacle strength and spacing on the slope of Haasen plot

The rate sensitivity of multiple obstacle aluminium alloy system was measured using the stress relaxation method. A discrepancy was observed between the slope of the Haasen plot (rate sensitivity of dislocation–dislocation interaction) in pure metals and in alloys strengthened by multiple obstacles. Considering a simplifying assumption of the constant obstacle force–distance profile, it is suggested that slope of the Haasen plot is governed by glide dislocations’ length taking part in a thermally activated event. The relative strength and spacing of obstacles (forest dislocations, solutes and precipitates) is proposed to affect the thermally activated dislocation length, which in turn manifests as the difference in slope of the Haasen plot.     

Slow feature analysis for monitoring and diagnosis of control performance

Recently, slow feature analysis (SFA), a novel dimensionality reduction technique, has been adopted for integrated monitoring of operating condition and process dynamics. By isolating temporal behaviors from steady-state information, the SFA-based monitoring scheme enables improved discrimination of nominal operating point changes from real faults. In this study, we demonstrate that the temporal dynamics is an additional indicator of control performance changes, and further exploit its unique efficacy in control performance monitoring. Because of its data-driven nature and ease from first-principle knowledge, the SFA-based monitoring scheme allows an overall assessment of the plant-wide control performance and is compatible with different control strategies. An attractive feature of the SFA-based approach compared to existing ones is that generic process monitoring indices are used, which renders contribution plots naturally applicable to real-time diagnosis of control performance. As a result, potential fault variables as root causes of control performance changes can be identified, including not only controlled variables (CV) but also manipulated variables (MV) and disturbance variables (DV). Simulated and experimental studies demonstrate the effectiveness of the proposed method.     

狭长地块上的建筑空间利用--以建屋9号地块配套商业为例

盘活边角地带、狭长地块，既考虑与地块内部主要功能区域的合理结合，又与周边城市空间做到自然接入，注重空间的整合与合理运用。     

Effect of calcination temperature on Cu doped NiO nanoparticles prepared via wet-chemical method: Structural,optical and morphological studies

In the present study, NiO and Cu-doped NiO nanoparticles were successfully synthesized by wet chemical method at room temperature using sodium hydroxide (NaOH) as precipitating agent. The as-prepared Cu-doped NiO powder samples were subjected to three different calcination temperatures such as, 350 °C, 450 °C and 550 °C in order to investigate the impact of calcined temperatures on the phase formation, particle size and band gap evolution. The phase formation and crystal structure information of the prepared nanomaterials were examined by X-ray powder diffraction (XRD). XRD revealed the face-centered cubic (FCC) structure. Average crystalline size of pure and doped samples estimated using Scherer formula was found to be 15 nm and 9 nm respectively. With increase in the calcination temperature from 350 °C to 550 °C for the Cu doped NiO samples the particle size of the nanoparticles was found to increase from 4 nm to 9 nm respectively. The optical study for both pure and doped NiO nanoparticles was performed using an UV–Vis spectrophotometer in the wavelength range of 200–800 nm. The strong absorption in the UV region confirms the band gap absorption in NiO and was estimated from the UV–Vis diffuse reflectance spectra via Tauc plot. Systematic studies were also carried out to study the effect of calcination on the optical transmittance. Samples were also investigated using Raman and Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, morphology of the pure NiO and Cu-doped NiO Nanoparticles were examined by scanning electron microscope (SEM).     

An approach to the evaluation of multivariate data during ball end milling free-form surface fragments

We present a method for investigating the process of ball end milling, a technology widely used in tool making and moulding. We analyse the main features of free-form surfaces used in this technology, and propose a sequence of steps to identify the most suitable milling strategy. The basic idea of such a sequence lies in the definition of the tangible fragments of free-form surfaces applicable to tool making. Tangible fragments represent the parts of tooling and signed radii that can distinguish both the active and transitional surfaces of tooling. Free-form surface fragments were selected since they are capable of securing definiteness in measurement of roughness parameters and surface errors. We investigated the operation capability of solid ball end milling cutters in terms of cutting tool edge micro-geometry. Cutting edge radius (r_n) and roughness parameters of the tool edge were measured to determine the relationship between new and worn tool edges. Roughness parameters were measured at different parts of the machined surfaces, which take on typical features of dies and moulds, such as inclined wall, ridge lines, valley lines, as well as, the active surfaces defined by signed radii. Surface error such as scallop height, gouging, tolerances and actual signed radii were measured at transitive surfaces. The traditional approach of evaluating roughness parameters was used to determine the suitability of factors such as milling operation, milling strategy and direction of milling. In addition, traditional approaches such as relationships, distributions and histograms were also used. We applied Khattree–Naik’s plot, which proves its suitability to visualise all the data being measured in the same units: microns and millimetres. Characteristic features of the ball end milling process, such as tool edge micro-geometry, geometry of the machined surface, and unit length of the transitive surface were applied in Khattree–Naik’s plots. We found that this plot was capable of processing multivariate data to distinguish specific markers of the quality of machined surfaces, which are produced in ball end milling.     

Dielectric properties of Sr0.5Ca0.5TiO3: x Pr3+ ceramics

The frequency dependent dielectric and AC conductivity properties of different concentrations of Pr³⁺ doped Sr_0.5Ca_0.5TiO₃ ceramics were investigated for the frequency range 100 Hz to 2 MHz at different temperatures. The morphology of the prepared samples was analyzed by using Field-Emission Scanning Electron Microscope images. The value of dielectric constant and dielectric loss decreases with increase in the frequency of the applied signal in all the samples. Also, the value of dielectric constant and dielectric loss decreased with doping of different concentrations of Pr³⁺ ions. The conductivity of the samples obeys Jonscher's power-law and shows a decrease with increasing doping concentration of Pr³⁺ ions. The higher value of real and imaginary part of impedance at lower frequency indicates the space charge polarization of the material and its absence at higher frequencies was confirmed from the low value of impedance at higher frequency region. The Cole- Cole parameters of the samples were calculated and the semi-circle observed indicates a single relaxation process and can be modeled by an equivalent parallel RC circuit. At lower frequency region, the value of dielectric constant and dissipation factor increases with increase in the temperature. Also the value of conductivity increases with temperature at high frequency region, due to the enhanced mobility of charge carriers.     

不同生态护坡下水土保持效果动态变化研究

为研究不同生态护坡措施实施后其护坡效果随时间的变化情况,选取北京市昌平区朱辛庄水土保持示范基地内的4组不同护坡类型径流小区为研究对象,通过连续5 a的植被调查和人工模拟降雨实验研究,对各个护坡径流小区的植被状况以及产流和产沙数据进行了分析。结果显示:4种生态护坡实施后,随着时间推移,护坡植物种类会朝着当地土生植物种类发生演替,从而导致护坡的水土保持效果发生变化,每种生态护坡的效果各不相同;单一植物护坡容易受到植物演替规律的影响,而采用工程与植物措施相结合的护坡形式,水土保持效果则更为持久有效。研究成果可为今后生态护坡技术的推广应用提供借鉴。     

单元嵌套网格产汇流理论

凭借"大数据"可以精细刻画降雨空间分布和下垫面空间变异性的优势,提出了"大数据"背景下考虑降雨空间分布和下垫面空间变异性对流域产汇流影响的计算方法,即单元嵌套网格剖分流域的方法。通过引入"网格水滴"的概念揭示了流域瞬时单位线的物理本质,对由RodriguezIturbe和Valdes所提出R-V地貌瞬时单位线理论进行补充,分析了等流时线法和单位线法的局限性,提出的单元嵌套网格产汇理论既克服了等流时线法和单位线法的缺点,也吸取了它们的优点,为在"大数据"支撑下统一等流时线和单位线法提供了可行性。     

汾河上游水文干旱时空演变特征分析

以汾河上游四个水文站月径流资料为基础,选取常用的六种概率分布拟合了月、季、年时间尺度下的径流量,并进行了拟合优度检验,判断出汾河上游水文站不同时间尺度下径流服从的最佳分布函数,根据最佳分布函数计算标准化径流指数,分析不同时间尺度下的水文干旱时空变化特征。结果表明,汾河上游不同站点在不同时间尺度下服从的概率分布并不统一;不同时间尺度下四个水文站的标准化径流指数变化具有较好的一致性;1956~2000年标准化径流指数总体呈下降趋势,水文干旱逐年加重;西北部干旱程度逐渐减轻,东南部干旱严重程度逐渐加重。