Numerical simulation of rock salt dissolution in dynamic water

The dissolution process of the rock salt is actually a complicated process in fluid dynamics and chemical kinetics; therefore, the mathematical model for the solute-fluid flow during the cavern building may be established to research the change rule of the form of the cavern boundary based on the kinetic analysis of the convection–diffusion process, with integration of the basic theories of fluid mechanics and the principles of chemical kinetics. In order to research the dissolution mechanism of the rock salt under the condition of dynamic water, the method of numerical simulation has been employed to simulate and study the factors with effect on the fluid transport mechanism in solution mining cavern of the rock salt, and its dissolution in dynamic water has been simulated and researched. The result shows that the model established in this paper may well describe the dissolution process of rock salt under the condition of dynamic water, providing basic analyzing means for the research on the rock salt dissolution in dynamic water.     

Ensemble estimates of the wave state related parameters in a sea spray parameterization scheme

Ocean Dynamics - Uncertainties of the wave state parameters in a sea spray parameterization scheme can be a major source of errors for air-sea turbulent (momentum, sensible and latent) fluxes...     

流空间视角下中国城市群网络结构特征比较——基于铁路客运班次的分析

铁路客流是城市群内经济社会联系的重要反映,也是区域流空间的关键体现。本文依据流空间理论,采用复杂网络方法和2018年中国铁路班次OD数据,从全国尺度分析城市群社区结构特征,并从城市群尺度比较分析了5个主要城市群的空间结构、规模结构和网络节点结构。结果显示,从铁路客运班次联系来看,城市组团片区与国家规划方案中的城市群在范围上存在一定的空间错位。5个主要城市群具有不同的局部特征：① 长江三角洲城市群呈网络状的空间形态和相对集聚的规模分布,主要问题为局部节点的枢纽作用与规模的匹配性有待提高;② 珠江三角洲城市群呈放射状的空间形态和相对集聚的规模分布,主要问题为与全国其他城市群的联系相对薄弱;③ 京津冀城市群呈放射状的空间形态和相对集聚的规模分布,主要问题为存在边缘化的节点;④ 长江中游城市群呈组团状的空间形态和相对分散的规模分布,主要问题为内部结构较为松散;⑤ 成渝城市群呈哑铃状的空间形态和相对集聚的规模分布,主要问题为与全国其他城市群的联系薄弱。随着区域一体化进程,需要根据不同城市群网络结构发展阶段的差异,补足城市群内和城市群间的联系短板,促进规模位序结构与网络结构的耦合协调,推动建设层次分明、枢纽协作、网络化发展的客运服务网络,支撑城市群一体化发展。     

Neolithic agriculture, freshwater resources and rapid environmental changes on the lower Yangtze, China

Analyses of sedimentary evidence in the form of spores, pollen, freshwater algae, dinoflagellate cysts, phytoliths and charcoal from AMS ¹⁴C-dated, Holocene-aged sequences provide an excellent opportunity to examine the responses of Neolithic agriculturalists in the lower Yangtze to changing environments. Evidence from two sites close to the southern margin of the Yangtze delta and separated by what is now Hangzhou Bay attests the critical importance to early attempts at food production of access to freshwater resources. More readily, if episodically, available freshwater resources during the early to mid-Holocene on the Hangjiahu plain may have encouraged an early reliance on rice-based agriculture, which in turn facilitated the accumulation of agricultural surpluses and cultural diversification. Cultural change was relatively attenuated and human population pressures possibly lower on the Ningshao plain, seemingly because of much more profound environmental impacts of variations in local hydrological conditions, and because predominantly saline conditions, associated with rising relative sea level, hampered the early development of irrigated agriculture. The evidence, although largely dating to the early and middle parts of the Holocene, provides a timely warning of the complexity of vulnerability to climate change-induced processes of agriculture, and indeed human activities more generally, on megadeltas in Asia.     

Hydroxyl and Peroxy Radical Chemistry in a Rural Area of Central Pennsylvania: Observations and Model Comparisons

Atmospheric hydroxyl (OH), hydroperoxy (HO₂), total peroxy (HO₂ and organic peroxy radicals, RO₂) mixing ratios and OH reactivity (first order OH loss rate) were measured at a rural site in central Pennsylvania during May and June 2002. OH and HO₂ mixing ratios were measured with laser induced fluorescence (LIF); HO₂ + RO₂ mixing ratios were measured with chemical ionization mass spectrometry (CIMS). The daytime maximum mixing ratios were up to 0.6 parts per trillion by volume (pptv) for OH, 30 pptv for HO₂, and 45 pptv for HO₂ + RO₂. A parameterized RACM (Regional Atmospheric Chemistry Mechanism) box model was used to predict steady state OH, HO₂ and HO₂ + RO₂ concentrations by constraining the model to the measured OH reactivity and previously measured volatile organic compound (VOC) distributions. The averaged model calculations are generally in good agreement with the observations. For OH, the model matched the observations for day and night, with an average observed-to-modeled ratio of 0.80. In previous studies such as PROPHET98, nighttime NO was near 0 pptv and observed nighttime OH was significantly larger than modeled OH. In this study, nighttime observed and modeled OH agree to within measurement and model uncertainties because the main source of the nighttime OH was the reaction HO₂ + NO → OH + NO₂, with the NO being continually emitted from the surrounding fertilized corn field. The observed-to-modeled ratio for HO₂ is 1.0 on average, although daytime HO₂ is underpredicted by a factor of 1.2 and nighttime HO₂ is over-predicted by a factor of ∼2. The average measured and modeled HO₂ + RO₂ agree well during daytime, but the modeled value is about twice the measured value during nighttime. While measured HO₂ + RO₂ values agree with modeled values for NO mixing ratios less than a few parts per billion by volume (ppbv), it increases substantially above the expected value for NO greater than a few ppbv. This observation of the higher-than-expected HO₂ + RO₂ with the CIMS technique confirms the observed increase of HO₂ above expected values at higher NO mixing ratios in HO₂ measurements with the LIF technique. The maximum instantaneous O₃ production rate calculated from HO₂ and RO₂ reactions with NO was as high as 10–15 ppb h⁻¹ at midday; the total daily O₃ production varied from 13 to 113 ppbv d⁻¹ and was 48 ppbv d⁻¹ on average during this campaign.     

Research on elastoplastic damage constitutive model of intact Q2l loess in northwestern of China

Based on the unsaturated triaxial experiments for the intact fourth period Middle Pleistocene Epoch loess (Q₂l loess), the mechanical characteristic of Q₂l loess is studied. According to the continuum damage mechanics and elastic–plastic theory, the damage potential function and loading function were deduced. Besides, plastic deformation and irreversible damage deformation are supposed to obey Hyushin’s postulate. The elastoplastic damage constitutive model and damage evolution law of the unsaturated intact Q₂ loess are set up. Comparing the experiment curves with the computation result of this model, it is shown that the model can stimulate the mechanics characteristics of Q₂ loess well.     

邢台地震区浅部构造特征及其与深部构造的耦合关系

根据邢台7-2 级和6-8 级地震震中区的浅层和超浅层地震勘探结果,查明了震中区浅部铲形断裂的性质及活动年代,认为新河断裂(F1) 自晚更新世以来已不再活动,它不是发震断裂。另外,结合该区深地震反射剖面和深地震测深剖面结果,讨论了震中区的深浅部构造形态及它们的相互关系,从而确定了发震断裂应为震源之下的高倾角超壳断裂①。邢台地震的发生是由于地幔岩浆的上侵作用产生附加应力场,并与区域构造应力场共同作用使该断裂重新活动,引发了邢台地震,并引起浅部断层及地表物质的运动     

某区放射性环境地质评价研究

在某区拟建隧洞沿线的条带状区域进行了放射性环境地质调查。共采集和分析岩土(芯)放射性核素镭、钍、钾样品111组,地下水和地表水样品5组;现场测定岩土放射性样品392组。结果表明,在该区域内,某煤矿巷道中煤层和砂岩接触带煤、砂岩中镭-226比活度出现高值异常,相应的内照射指数和外照射指数也超过相关标准中规定的放射性核素限量,该异常带环境辐射剂量率也较高。镭-226的富集可能源于煤中有机质对放射性核素的吸附和解吸过程。建议在隧道选线过程中尽力避让这一地段。     

A dynamic dissolution model of rock salt under gravity for different flow rates

The dissolution mechanism of rock salt under the effect of gravity was investigated in the laboratory using a dynamic dissolution test apparatus. Rock salt specimens were subjected to dissolution at different flow rates and the weight of the dissolved salt was measured over time and a comparison between the dissolution weight changes under the effect of gravity of this paper and those of dissolution without considering the gravitational effect was analyzed. After introducing the partial differential equations of a dynamic dissolution which conducted in a non-gravity condition, the influence of different parameters on the dissolution model was discussed to establish the dynamic dissolution model of rock salt under gravitational effect. Then, a numerical solution based on the finite-difference method and parameter inversion was conducted, whose numerical calculation results were in good agreement with the experimental results. The results of this paper can provide a basic theoretical foundation and analytical means that can serve a guide for studies on the dissolution mechanism of rock salt.     

基于观测和再分析数据的LSTM深度神经网络沿海风速预报应用研究

基于海洋气象历史观测资料和再分析数据等,利用LSTM深度神经网络方法,开展在有监督学习情况下的海面风场短时预报应用研究。以中国近海5个代表站为研究区域,通过气象台站观测数据和ERA-Interim 6 h再分析数据构建数据集。选取21个变量作为预报因子,分别构建两个LSTM深度神经网络框架(OBS_LSTM和ALL_LSTM)。经与2017年WRF模式6 h预报结果对比分析,得出如下结论:构建的两个LSTM风速预报模型可以大幅降低风速预报误差,RMSE分别降低了41.3%和38.8%,MAE平均降低了43.0%和40.0%;风速误差统计和极端大风分析发现,LSTM模型能够抓住地形、短时大风和台风等敏感信息,对于大风过程预报结果明显优于WRF模式;两种LSTM模型对比发现,ALL_LSTM模型风速预报误差最小,具有很好的稳定性和鲁棒性,OBS_LSTM模型应用范围更广泛。