Investigation on new color depth formulas

Color depth is difficult to evaluate; however, it plays an important role in the assessments of color fastness, dyeing properties, and so on. The subjective evaluation of color depth is prone to be affected by people, environment, etc. As for objective evaluation, there are more than 10 formulas, which confuses the user. In this study, a theoretically designed new formula is inspected through 18195 chips with 24 grades of color depth from the SINO COLOR BOOK, with the help of four preferable objective evaluation formulas. The specimens were measured using an X‐Rite Color i7 spectrophotometer, and all their depth values were calculated and statistically analyzed by programming MATLAB. Of the five formulas, the new formula yields the best outcome of variance coefficients (CVs) but the worst linearity, with a correlation coefficient R = 0.976. It was then theoretically revised to two other formulas, one obtains the highest linearity (R = 0.9997) and the third CV, and the other gains the second linearity (R = 0.9984) and the second CV among the seven formulas. Besides, the three new formulas are not as sensitive as the others to the changes of Hue and Chroma. In general, the new revised formulas show potential and need to be further evaluated.     

2011～2020年华北平原气溶胶光学厚度时空分布特征及潜在源分析

随着经济高速增长和城市化进程不断加快,华北平原区域性空气污染问题愈演愈烈。针对该区域开展长时序气溶胶光学厚度时空分布特征和潜在源分析研究,对华北平原大气污染治理具有重要意义。基于长时序MODIS/Terra C6.1 MOD04_L2气溶胶光学厚度产品,分析华北平原气溶胶光学厚度的时空分布特征,并利用后向轨迹聚类分析讨论华北平原7个重点城市气团输送的季节变化,并以污染较为严重的河北石家庄为例进行潜在源分析和浓度权重分析,探究影响其大气质量的污染物潜在源区。结果表明:2011～2020年华北平原气溶胶光学厚度月均值呈显著的周期性变化,以年为周期,每个周期内峰值一般出现在6月至8月; 气溶胶光学厚度月际年内呈单峰分布,峰值出现在6月(0.75),最小值出现在12月(0.37); 气溶胶光学厚度季均值从大到小依次为夏季(0.67)、春季(0.59)、冬季(0.49)、秋季(0.46); 10年间气溶胶光学厚度呈下降趋势,整体下降幅度达36.84%,其中2011年最高(0.72),2018年最低(0.45); 华北平原7个重点城市春、夏、秋、冬四季主要受短距离气团输送影响较大,长距离气团输送影响较小; 2014～2020年河北石家庄的空气质量优良天数占比相对较小,空气质量状况差,影响其空气质量的污染物多为本地生成,同时也受周边省市近距离输送的影响。     

Application of large scale PIV in river surface turbulence measurements and water depth estimation

Large-Scale Particle Image Velocimetry (LSPIV) has emerged as a reliable technology to measure river surface flow velocity distribution and can be applied to estimate river discharge. Fewer studies have explored the capability of surface turbulence measurements using LSPIV. In this paper, LSPIV is applied to evaluate statistics of surface turbulence of a natural river. Turbulence measurements including velocity fluctuation, velocity spectra and the dissipation rate of turbulent kinetic energy (TKE) are validated by comparing with those measured by an Acoustic Doppler Velocimeter (ADV). Traditionally, estimation of stream discharge through LSPIV needs a secondary measurement to determine river bathymetry and water depth. A new method is presented here to demonstrate that for a fully developed and channel-controlled flow, the cross section geometry can be estimated from the combined measurements of surface mean velocity and the dissipation rate, following the Manning-Strickler formula. Therefore, river discharge can be estimated with LSPIV along with a calibrated Manning's roughness, without additional bathymetry survey. The proposed new method is applied to measure discharge in Milwaukee River (Milwaukee, Wisconsin, U.S.A.), which agreed well with data obtained from a nearby streamgage station.     

A novel and exact analytical model for determination of critical depth in trapezoidal open channels

Critical depth is a significant parameter in the designing and management of open channels and related hydraulic structures, understanding the flow characteristics and calculations of varied flows (gradually, spatially, etc.). The trapezoidal cross sections are the most commonly used geometric sections in the network of water transmission and distribution channels, thus discussing its geometrical and hydraulic parameters is inevitable. The used nonlinear and mathematical relationships governing the critical depth problem in the trapezoidal channels are implicit and complex, hence the methods of trial and error, graphical and numerical are used to calculate it. In the present study, new explicit equations are presented based on mathematical analysis of the critical depth problem in the trapezoidal channel. Mathematical analysis has led to completely mathematical and analytical solutions having a definite physical (hydraulic) concept. Having the explicit equations provided by the ease of calculation process with no limitation of the application range and high accuracy are the advantages of this analysis. The accuracy of the presented equations is desired and determined according to the required accuracy. The data used for verification of the results are based on the critical flow condition (Froude number equal to 1), which has been generated in a wide and practical range of the geometric and hydraulic characteristics of the channel. Also, the calculated values are compared with the real values of the considered parameter.     

Hydraulics of free overfall in steeply sloping rough rectangular channel: A general computational approach

All supercritical free overfalls were almost considered as frictionless flow or pseudo-uniform flow before, the effect of friction had not been paid due attention. Currently, a new mathematical model is proposed to analyze supercritical rectangular free overfall by Boussinesq-type energy equation accounting for frictional effect. A computational approach of loop iteration algorithm is utilized to simultaneously calculate the implicit water surface profile by Runge-Kutta method, end-depth-ratio, and discharge. Subsequently, the dependency of discharge on end depth and Nikuradse equivalent sand roughness for different slope is illustrated. Comparison of computed results with experimental observations reveals satisfactory agreement. Additionally, the present energy approach leads to more accurate results than the momentum method for high roughness. Finally, to aid application for engineers, an explicit solution of discharge for practical application in the commonly using range is also proposed. The most important purpose of this study is to present a general computational approach, which could be used for the rough supercritical free overfalls of any other cross-sections.     

Decomposition and replacement: Spatial knowledge distillation for monocular depth estimation

Knowledge distillation has become a key technique for making smart and light-weight networks through model compression and transfer learning. Unlike previous methods that applied knowledge distillation to the classification task, we propose to exploit the decomposition-and-replacement based distillation scheme for depth estimation from a single RGB color image. To do this, Laplacian pyramid-based knowledge distillation is firstly presented in this paper. The key idea of the proposed method is to transfer the rich knowledge of the scene depth, which is well encoded through the teacher network, to the student network in a structured way by decomposing it into the global context and local details. This is fairly desirable for the student network to restore the depth layout more accurately with limited resources. Moreover, we also propose a new guidance concept for knowledge distillation, so-called ReplaceBlock, which replaces blocks randomly selected in the decoded feature of the student network with those of the teacher network. Our ReplaceBlock gives a smoothing effect in learning the feature distribution of the teacher network by considering the spatial contiguity in the feature space. This process is also helpful to clearly restore the depth layout without the significant computational cost. Based on various experimental results on benchmark datasets, the effectiveness of our distillation scheme for monocular depth estimation is demonstrated in details. The code and model are publicly available at : https://github.com/tjqansthd/Lap_Rep_KD_Depth.     

电子探针面分析法测定钢的脱碳层深度

提出钢表层脱碳层深度测定的一种新方法,即电子探针面分析法。对热轧态高碳工具钢75Cr1、淬火齿轮钢20CrMnTi、冷轧退火低碳车厢板SH1100钢3个典型钢种完成脱碳层深度的测定试验,结果表明:对于珠光体-铁素体型中高碳钢的脱碳层深度测定,金相法测定值是电子探针面分析法测定值的77%左右;对于淬回火钢的脱碳层深度测定,电子探针面分析法的测量精度在10 μm以下,约是显微硬度法测量精度的十分之一;对于脱碳层深度不易准确测定的低碳钢,电子探针面分析法通过较大区域范围的平均碳含量变化曲线来测定脱碳层深度,测量结果准确。电子探针面分析法在脱碳层深度测定方面具有钢种组织状态不限、试样形状不限、数据统计性好、测量精度高、易操作等优势,可在业内大力推广。     

Performances of ideal wind turbine

If there is an ideal wind turbine, its performances will be the pursuit goals for designing the actual wind turbine. In this paper, the wind turbine that has the maximum efficiency is defined as ideal wind turbine, which has three main features: lift-drag ratio is infinite, it has enough number blades so that the blade tip and root losses can be ignored, and its blades are limited in width. Using blade element theory, the differential equations of power, torque, lift and thrust of blade element were derived, and the expressions of power, torque, lift and thrust coefficients of the ideal wind turbine were gained by integrating along the blade span. Research shows that the power, torque and lift coefficients of the ideal wind turbine are functions of tip-speed ratio. When the lift-drag ratio and the tip-speed ratio is approaching infinity, power coefficient of the ideal wind turbine is close to the Betz limit; The torque limit is 0.401 when the tip-speed ratio equals about 0.635; The Lift limit is 0.578 when the tip-speed ratio equals about 0.714; The thrust coefficient is 8/9, which is unrelated with tip-speed ratio. For any wind turbine which tip-speed ratio is less than 10, the power coefficient is unlikely to exceed 0.585, for any high-speed wind turbine which tip-speed ratio is greater than 6, the torque coefficient in steady state is unlikely to exceed 0.1, and the lift coefficient is unlikely to exceed 0.2.     

旋转式尿素造粒喷头的设计理论研究及工程应用

采用极限负荷准则,在考虑造粒喷头极限造粒能力的情况下,避开了尿素造粒喷头内复杂的流体力学问题的计算工作,给出了常压式旋转式尿素造粒喷头的参数确定方法。针对典型的年产400 kt尿素装置造粒喷头的设计过程及使用情况进行了计算,比较了斜孔喷头和直孔喷头在造粒塔内的不同喷洒效果,分析了众多文献中报道的塔内驼峰产生的原因和改进方向。在理论计算的基础上,讨论了带压式喷头和常压式喷头的工作原理和影响因素及各自在实际生产中的优缺点。     

综放工作面支承压力分布演化规律研究

针对综放工作面超前支承压力无法定量描述的问题,以大采高综放面极限平衡区煤体为主要研究对象,建立了超前支承压力作用下综放面前方煤体的力学模型,应用弹塑性极限平衡理论对超前支承压力进行研究。利用FLAC^3D数值模拟软件,模拟分析不同开挖距离下工作面前方支承压力演化规律,模拟分析所得支承压力值与理论分析结果趋近,为相似条件下超前支承压力分布规律的计算提供了理论基础。