断层防水煤柱可靠度分析

为了合理设计防水煤岩柱的宽度,使用了可靠度分析的“JC”方法,分析了水压力、煤层抗张强度及突水系数的不确定性,建立了防水煤柱可靠度分析的极限状态方程。并计算了与防水煤柱有关的可靠度指标、失效概率和安全系数。参考其它事故的死亡率,防水煤柱的失效概率为1× 10 -5~1× 10 -6比较合适。      

应力与变形的数值模型方法--数值模拟软件FLAC介绍

FLAC软件是进行应力与变形的一种专业软件，特别适合求解岩土力学工程中非线性的大变形问题，在地质构造及块体运动学、动力学研究中得到了广泛应用。本文主要介绍了FLAC应用软件的主要功能和特点以及它在国内外的应用现状。     

扩展型Boussinesq水波方程的混合求解格式

为高效求解扩展型Boussinesq水波方程,建立了基于有限差分和有限体积方法的混合数值格式。将一维控制方程写为守恒形式,方程中通量部分采用有限体积方法求解,剩余部分采用有限差分方法求解。其中,有限体积方法采用Godunov类高分辨率格式,并结合HLL(Harten-Lax and van Leer)式黎曼问题近似解求界面数值通量,黎曼问题界面左右变量通过高精度状态插值方法(MUSCL)构筑。有限差分方法则采用具有二阶精度的中心差分公式进行。采用具有TVD(Total Variation Diminishing)性质的三阶龙格-库塔多步积分法进行时间积分。对数值模式进行了验证,数值结果同解析解或实验数据吻合良好。     

流体-结构相互作用下用微分求积法求弹性板上的动水压力场

采用微分求积法(DQ)在流体-结构相互作用(FSI)框架下求解原变量形式的Navier-Stokes(N-S)方程和板的弯曲振动方程,获取作用在弹性板上的动水压力场.分析对象是4块矩形板组成的箱型流道,其中两块为弹性薄板,另外两块为刚性板.为比较FSI对动水压力场的影响,数值结果给出了1.5m×0.5m×0.2m流道、来流雷诺数分别为000和10000、相应DQ网格为25×25×25和29×29×29考虑FSI与否的压力分布.数值计算结果表明,所建立的考虑FSI的DQ法数值求解原变量形式N-S方程和弹性板振动方程,获取弹性板上的动水压力场是可行的,FSI效应对动水压力场的影响是明显的.     

Numerical simulation of colour equations for the uvby system

The results of numerical simulation of colour equations of uvby photometry for filter-defined bandpasses are presented. It is shown that linear transformation equations to the standard system are valid for instrumental systems deviating by no more than 2.5 nm in peak transmission wavelengths. The comparison with the results of observations is satisfying. Im Ergebnis einer numerischen Farbgleichungssimulation im uvby-System wird nachgewiesen, daß für Instrumentensysteme mit Abweichungen der Wellenlängen maximaler Transmission bis zu 2.5 nm gegenüber den Standardwerten eine lineare Transformation möglich ist. Der Vergleich mit Beobachtungsresultaten zeigt eine gute Übereinstimmung.     

Data augmentation for bias correction in mapping PM2.5 based on satellite retrievals and ground observations

As most air quality monitoring sites are in urban areas worldwide, machine learning models may produce substantial estimation bias in rural areas when deriving spatiotemporal distributions of air pollutants. The bias stems from the issue of dataset shift, as the density distributions of predictor variables differ greatly between urban and rural areas. We propose a data-augmentation approach based on the multiple imputation by chained equations (MICE-DA) to remedy the dataset shift problem. Compared with the benchmark models, MICE-DA exhibits superior predictive performance in deriving the spatiotemporal distributions of hourly PM_2.5 in the megacity (Chengdu) at the foot of the Tibetan Plateau, especially for correcting the estimation bias, with the mean bias decreasing from –3.4 µg/m³ to –1.6 µg/m³. As a complement to the holdout validation, the semi-variance results show that MICE-DA decently preserves the spatial autocorrelation pattern of PM_2.5 over the study area. The essence of MICE-DA is strengthening the correlation between PM_2.5 and aerosol optical depth (AOD) during the data augmentation. Consequently, the importance of AOD is largely enhanced for predicting PM_2.5, and the summed relative importance value of the two satellite-retrieved AOD variables increases from 5.5% to 18.4%. This study resolved the puzzle that AOD exhibited relatively lower importance in local or regional studies. The results of this study can advance the utilization of satellite remote sensing in modeling air quality while drawing more attention to the common dataset shift problem in data-driven environmental research.