井下气液混合输送技术研究

为了确保油田开采过程中电潜泵在高含气油井的正常运行,结合气液分离技术和引射技术,运用CFD模拟软件FLUENT研究了一种高含气井下气液混合输送技术。该技术通过建立气体及液体分采通道,利用引射原理将增压后的高压动力液携带富气流举升至地面,以实现利用生产井自身流体实现自我举升。研究表明:经过对比分析发现,对于不同入口气体含量的工况,由于射流泵引射器的引射比影响,入口气体体积含量40%是一拐点,当入口气体含量超过40%时,引管内的气相含量以及流速基本达到一定值;对于不同入口流量,随着流量的增加,气液分离效果亦逐渐变佳,取管内的气相含量基本稳定在一定的范围,而取气管内的流速则随着流量的增加而增大。该研究结果对提高电潜泵在油田开采高含气油井中的应用范围具有重要意义

高含气井下气液混合输送技术研究

为了确保油田开采过程中电潜泵在高含气油井的正常运行,结合气液分离技术和引射技术,该文运用CFD模拟软件FLUENT研究了一种高含气井下气液混合输送技术.该技术通过建立气体及液体分采通道,利用引射原理将增压后的高压动力液携带富气流举升至地面,以实现利用生产井自身流体实现自我举升.研究表明:经过对比分析发现,对于不同入口气体含量的工况,由于射流泵引射装置的引射比影响,入口气体体积含量40%是一拐点,当入口气体含量超过40%时,引管内的气相含量以及流速基本达到一定值;对于不同入口流量,随着流量的增加,气液分离效果亦逐渐变佳,取气管内的气相含量基本稳定在一定的范围,而取气管内的流速则随着流量的增加而增大.该研究结果对提高电潜泵在油田开采高含气油井中的应用范围具有重要意义

社会系统工程与国家治理体系现代化

2014年3月30日,中国人民大学国家发展与战略研究院社会系统工程研究中心成立暨“社会系统工程与国家治理体系现代化“学术研讨会在中国人民大学逸夫会堂第一会议室举行,来自十余所高校和学术团体的专家、学者和一些媒体的代表参加了会议。现把会议主要发言内容选载如下

Retrieval of aerosol optical depth over urban area by coupling the characteristics of surface directional reflection

Aerosols play an important role in determining the Earth's radiation budget and its impact on climate change. Aerosol optical depth (AOD) is a crucial fundamental parameter for meteorological observation and a basic optical property of aerosol derived from satellites. Over land, the aerosol contribution in satellite signals is small compared with the surface, making it difficult to separate the aerosol path radiance from satellite measurements, particularly over the urban area. In the past several decades, numerous different AOD retrieval algorithms have been proposed by using different satellite sensors, but most of them do not consider surface anisotropy. The main purpose of this work is to improve the accuracy of aerosol retrievals and reduce the uncertainty of the operational MODIS AOD products over mixed surfaces. On this basis, a new generic high-performance aerosol retrieval algorithm is presented and explained. The new method is developed by coupling the non-Lambertian atmospheric radiative transfer model and semiempirical linear kernel-driven BRDF model. First, an a priori surface BRDF shape parameter database is constructed using the daily MODIS BRDF/Albedo product by using penalized least square regression based on a 3D discrete cosine transform (DCT-PLS) method. Then, the estimation of surface reflectance, including bidirectional reflectance, directional to hemispheric reflectance, hemispheric to directional reflectance, and bihemispheric reflectance (also called white-sky albedo, WSA), is based on this database and kernel-driven BRDF model. The presented method is tested on the Landsat 8 OLI images around the Beijing area, which features highly heterogeneous surfaces and severe air pollution problems. AOD retrievals with 500 m resolution can be successfully obtained over dark and bright surfaces. An accuracy assessment of the new algorithm, WSA-derived and HARLS AOD retrievals against AERONET AOD, from the four selected stations indicated the superiority of new algorithm, which is reflected in the high PWE and low RMSE. The comparison results show that the new algorithm is in good agreement with ground-based AOD (R=0.911) compared with the WSA-derived and HARLS AOD retrievals. Furthermore, the new algorithm and MODIS aerosol algorithms have similar spatial patterns of AOD. The new algorithm significantly improves the accuracy of aerosol retrievals, which is verified by AERONET AOD data, especially over brighter surfaces, because surface anisotropy is considered in this algorithm. The new algorithm can provide a detailed AOD spatial distribution over mixed surfaces and shows high ability in capturing fine-scale features. The new algorithm and MAIAC AOD retrievals have a similar spread of uncertainty envelopes. However, the new algorithm AOD retrievals have a higher correlation and smaller RMSE than the MAIAC retrievals, and the number of collections with AERONET for the new algorithm is almost 1.5 times those for MAIAC. This new AOD retrieval algorithm can provide a possibility for high-precision urban aerosol remote sensing monitoring and solve other pressing issues, such as long-term trend analysis of urban aerosols and air quality conditions, especially in heavily polluted areas. Based on the collocated observations, the new algorithm achieved satisfactory retrieval accuracy. However, several issues remain to be solved in the future. First, the retrieval errors of the MODIS BRDF kernel parameters are also a major source of uncertainty. Second, more analyses of the aerosol models and model selection are required. Third, the application in other regions and sensors is required in further work to evaluate the applicability of new algorithm

SOI MOSFET I-V特性的计算机模拟

本文研究了SOI MOSFET的 I - V特性，建立了一套模拟SOI器件工作特性的解析模型，适用于不同的SOI膜厚和各种前、背栅的偏置情况，在各种不同情况下由计算机自动选择适当模型进行拟合，该模型物理意义明确，计算简便快速，所用参数易于提取。The I-V characteristics of SOI MOSFET are studied and an analytic model for SOI MOS devices is established. The model, which is valid for any SOI film thickness and each kind of front/back-gate bias conditions, has such advantages as analytic expression, clear physical meaning, simple and quick calculation, and easy extraction of used parameters. For each SOI film thickness or back gate bias, the suitable expression will be adopted automatically by the computer. The simulation results are well consistent with the experimental data

A Method for Constructing Underwater Topography in Coastal Zones While Accounting for Spatial Anisotropy: The Case of the Yellow River Delta

Bathymetric points are the main data source for obtaining high-quality underwater Digital Elevation Models (DEMs). The low density of bathymetric points in coastal zones can lead to low underwater DEM accuracy. To address this problem, we propose a multiparameter collaborative optimization algorithm for point densification that considers spatial anisotropy. First, the particle swarm optimization was employed to collaboratively optimize the four parameters affecting the computational accuracy to achieve the overall tuning and determine the optimal solutions of the four parameters. Subsequently, the four determined parameters were applied to the inverse distance weighting method to obtain in the global sense the optimal value of the complementary point depth. Finally, the proposed densification method was validated using four common interpolation methods in geosciences and bathymetric data from the coastal zone of the Yellow River Delta from 1992, 2007, and 2015. The experimental results showed that this method significantly improves the interpolation accuracy of the processed data, reducing both the absolute and relative errors by 12%. This method overcomes the problem of large interpolation errors caused by the density of bathymetric points and allows for a more accurate underwater topography reconstruction

黄河三角洲的地面沉降分析以及海水淹没预估

在全球气候变化背景下,不断上升的海平面和地面沉降使黄河三角洲面临着严峻的海水淹没风险,对未来黄河三角洲的可持续发展造成威胁。预估黄河三角洲由于地面沉降而造成的相对海平面变化有助于深入认识当前海水淹没风险,并可以及时采取措施应对。首先,基于小基线集干涉测量技术得到2016年2月至2019年9月的平均沉降速率,利用水准数据进一步提高InSAR结果精度,补偿后最大平均沉降速率达-357 mm/a,结合高分影像的目视解译发现地面沉降的主要原因为地下卤水和油气的开采。其次,结合沉降点分布发现自然沉积作用对沿岸沉降影响还在继续。最后,使用有源算法,结合地面沉降结果和IPCC AR6中SSP2-4.5情景下海平面上升高度的置信区间建立海水淹没模型。模型结果表明:以当前沉降速率,到2030年、2050年和2100年,海水淹没面积占比分别为6.76%~6.84%、10.81%~11.11%和28.71%~30.92%;当沉降速率降至当前速率的50%和25%时,海水淹没面积占比分别为5.84%~5.91%、8.20%~8.40%、19.05%~21.51%和5.34%、 6.60%~6.69%、9.89%~11.62%。与绝对海平面上升所带来的威胁相比,对沉降速率的遏制,将会大幅度降低海水淹没风险。海水淹没的土地类型主要为建筑用地、耕地、水体和盐田,随着时间推移,建设用地、耕地和水体的海水淹没速率将不断加快。研究结果可为相关部门用于治理黄河三角洲水土资源开发与灾害防治提供参考

黄河三角洲的地面沉降分析以及海水淹没预估

在全球气候变化背景下,不断上升的海平面和地面沉降使黄河三角洲面临着严峻的海水淹没风险,对未来黄河三角洲的可持续发展造成威胁。预估黄河三角洲由于地面沉降而造成的相对海平面变化有助于深入认识当前海水淹没风险,并可以及时采取措施应对。首先,基于小基线集干涉测量技术得到2016年2月至2019年9月的平均沉降速率,利用水准数据进一步提高InSAR结果精度,补偿后最大平均沉降速率达-357 mm/a,结合高分影像的目视解译发现地面沉降的主要原因为地下卤水和油气的开采。其次,结合沉降点分布发现自然沉积作用对沿岸沉降影响还在继续。最后,使用有源算法,结合地面沉降结果和IPCC AR6中SSP2-4.5情景下海平面上升高度的置信区间建立海水淹没模型。模型结果表明:以当前沉降速率,到2030年、2050年和2100年,海水淹没面积占比分别为6.76%~6.84%、10.81%~11.11%和28.71%~30.92%;当沉降速率降至当前速率的50%和25%时,海水淹没面积占比分别为5.84%~5.91%、8.20%~8.40%、19.05%~21.51%和5.34%、 6.60%~6.69%、9.89%~11.62%。与绝对海平面上升所带来的威胁相比,对沉降速率的遏制,将会大幅度降低海水淹没风险。海水淹没的土地类型主要为建筑用地、耕地、水体和盐田,随着时间推移,建设用地、耕地和水体的海水淹没速率将不断加快。研究结果可为相关部门用于治理黄河三角洲水土资源开发与灾害防治提供参考