Spatial-temporal modeling of initial COVID-19 diffusion: The cases of the Chinese Mainland and Conterminous United States

COVID-19 outbreaks in China in late December 2019, then in the United States (US) in early 2020. In the initial wave of diffusion, the virus respectively took 14 and 33 days to spread across the provinces/states in the Chinese mainland and the coterminous US, during which there are 43％ and 70％ zero entries in the space-time series for China and US respectively, indicating a zero-inflated count process. A logistic growth curve as a function of the number of days since the first case appeared in each of these countries accurately portrays the national aggregate per capita rates of infection for both. This paper presents two space-time model specifications, one based upon the generalized linear mixed model, and the other upon Moran eigenvector space-time filtering, to describe the spread of COVID-19 in the initial 19 and 58 days across the Chinese mainland and the coterminous US, respectively. Results from these case studies show both models shed new light on the role of spatial structures in COVID-19 diffusion, models that can forecast new cases in subsequent days. A principal finding is that describing the spatio- temporal diffusion of COVID-19 benefits from including a hierarchical structural component to supplement the commonly employed contagion component.     

四川盆地焦石坝地区龙马溪组页岩气不同传输类型的临界孔径与传输能力

页岩气的扩散和渗流是页岩气富集过程中非常重要的地质作用,在地层条件下页岩气以扩散和渗流形式在微—纳米孔隙网络中进行传输。本文以四川盆地焦石坝地区龙马溪组页岩气藏为研究对象,基于克努森数与气体吸附机理,明确了页岩气扩散和渗流的主要类型;进一步结合气体微观分子动力学模拟,明确了剖面上不同页岩气扩散和渗流类型的临界条件;基于达西公式与菲克公式基本物理定义,建立了扩散系数与渗透率的关系,结合焦石坝地区龙马溪组页岩不同孔径下孔隙体积权重,查明了页岩全孔径视测渗透率的分布特征。研究表明,页岩气在地下主要存在三种扩散与两种渗流形式,包括吸附气表面扩散、克努森扩散、菲克扩散、滑脱渗流和达西渗流,现今焦石坝地区5种扩散和渗流类型临界孔径依次为1.2 nm、1.6 nm、25.0 nm、225.0 nm,不同扩散和渗流形式对应的孔隙体积占比依次为15.3%、5.6%、60.7%、6.4%、12.0%;宏孔主要提供了气体渗流空间、微孔与中孔主要提供了气体扩散空间,渗流传输能力约为扩散传输能力的10⁶倍。     

Study on effect of surface roughness on overland flow from different geometric surfaces through numerical simulation

Effect of variability in surface roughness on overland flow from different geometric surfaces is investigated using numerical solution of diffusion wave equation. Three geometric surfaces rectangular plane, converging and diverging plane at slopes 1 to 3% are used. Overland flow is generated by applying rainfall at constant intensity of 10 mm/h for period 30 min and 100 min. Three scenarios of spatial roughness conditions viz. roughness increasing in downstream direction, roughness decreasing in downstream direction and roughness distributed at random are considered. Effect of variability of roughness on overland flow in terms of depth, velocity of flow and discharge along the distance from upstream to downstream for different geometric surfaces are discussed in detail. Results from the study indicate that roughness distribution has significant effect on peak, time to peak and overall shape of the overland flow hydrograph. The peak occurs earlier for the scenario when roughness increases in downstream direction as compared to scenario when roughness is decreasing in downstream for all three geometric surfaces due to very low friction factor and more velocity at the top of the domain. The converging plane attains equilibrium state early as compared to rectangular and diverging plane. Different set of random values result in different time to peak and shape of hydrograph for rectangular and diverging plane. However, in case of converging plane, the shape of computed hydrographs remains almost similar for different sets of random roughness values indicating stronger influence of converging geometry than effect due to variation of roughness sequence on computed runoff hydrograph. Hierarchically, the influence of geometry on overland flow is stronger than the influence of slope and the influence of slope is stronger than the influence of roughness. Copyright © 2013 John Wiley & Sons, Ltd.     

An automated method for the calculation of P–T paths from garnet zoning,with application to metapelitic schist from the Kootenay Arc,British Columbia,Canada

An automated method for the calculation of P–T paths based on garnet zoning is presented and used to interpret zoning in metapelitic schist from the southern Canadian Cordillera. The approach adopted to reconstruct the P–T path is to match garnet compositions along a radial transect with predictions from thermodynamic forward models, while iteratively modifying the composition to account for fractional crystallization. The method is applied to a representative sample of garnet‐ and staurolite‐bearing schist from an amphibolite facies Barrovian belt in the southern Canadian Omineca belt. Garnet zoning in these schists is concentric and largely continuous from core to rim. Three zones are present, the first two of which coincide with sector‐zoned cores of garnet crystals. Similar zoning is developed in rocks that contain or lack staurolite, respectively, suggesting garnet growth was restricted to the initial part of the prograde P–T path prior to the development of staurolite. Growth zoning in large garnet crystals has not been significantly modified by diffusion. This interpretation is based on zoning characteristics of garnet crystals and is further supported by results of a forward model incorporating the effects of simultaneous fractional crystallization and intracrystalline diffusion. The P–T path calculated for this rock includes an initial, linear stage with a high dP/dT, and a later stage dominated by heating. The approach adopted in this study may have application to other garnet‐bearing rocks in which growth zoning is preserved.     

富氧空气/甲烷对向流扩散火焰的实验研究

为了开发实际适用的富氧燃烧技术,本研究对对向流扩散火焰这一典型的扩散燃烧形态为对象进行实验考查,发现得到的实验结果与作者先前进行的数值模拟结果得到比较好的吻合,即利用详细的基元反应动力学模型对火焰的数值模拟可以很好的再现火焰特性;在此基础上利用CCD成像技术进一步研究了燃料稀释浓度、氧化剂浓度的变化对富氧空气/甲烷对向流扩散火焰形态的影响规律。     

Eruptive and emplacement mechanisms of widespread fine-grained pyroclastic deposits on Vulcano Island (Italy)

 Tufi di Grotte dei Rossi Inferiori are thick ash deposits, representing the most voluminous stratigraphic unit on Vulcano Island. The deposits are related to hydromagmatic eruption which occurred under shallow water inside a caldera depression. Grain-size data and results of SEM investigation allow the character of the transporting medium, solid material concentration in the cloud during the lateral expansion, and the nature and role of the fluids present at the time of deposition to be constrained. We suggest that the eruption was characterized by closely timed hydromagmatic pulses giving rise to eruption clouds rich in water vapor and steam. The coarser material was not significantly transported in the eruptive cloud and it probably deposited in the caldera depression area. The finer material was extensively transported in the cloud, creating turbulent flows which surmounted the caldera rim barrier and dispersed in a southward direction, forming widespread deposits in the Piano area. Lower concentrated flows produced laminated deposits of more limited dispersion, whereas higher concentrated flows formed more dispersed thicker massive layers. Received: 26 February 1996 / Accepted: 17 June 1997     

Temperature–time path for the low-pressure Ryoke metamorphism, Japan, based on chemical zoning in garnet

Garnet crystals from low-pressure/high-temperature (LPHT) Ryoke metamorphic rocks in the Yanai district, south-western Japan, show several kinds of chemical zoning patterns that systematically vary with grain radius between c . 0.1 and 0.5  mm. Large grains (> c . 0.4  mm) show normal zoning and small grains (< c . 0.4  mm) show unzoned or reversely zoned cores. Observations of the chemical zoning and of the spatial and size distributions of the garnet grains between c . 0.1 and 0.5  mm in radius suggest that they were formed by continuous nucleation and diffusion-controlled growth.
A previously estimated temperature–time path ( T  – t path) for the Ryoke metamorphism, using 1-D numerical simulation, is characterized by a rapid increase in temperature, 0.0017  °C yr⁻¹ on average, and a period of high temperature (>600  °C) shorter than 0.5 Myr, which was presumably caused by the intrusion of a granodiorite sheet. Chemical zoning of garnet grains with different radii simulated for the T  – t path using a numerical model of continuous nucleation and diffusion-controlled growth, in combination with intracrystalline diffusion, compares well with the observed zoning patterns in garnet grains with different radii. This is in spite of the fact that the simulated zoning patterns vary greatly, depending on subtle differences in the T–t history. Therefore, they suggest that the T–t path gives a good explanation for the LPHT Ryoke metamorphism. Although this study only refers to the Ryoke metamorphism, the technique may be applicable to thermal modelling of other metamorphic terranes.     

激光测烟雷达探测烟气抬升的初步研究

本文分析了在山西某电厂进行的大气环境测试中用两部激光测烟雷达同时分段对210米烟囱排放的烟羽探测的资料,并对几个常用的、有代表性的烟气抬升高度计算式进行了比较分析。实测数据表明:在近中性类稳定度条件下的烟流抬升路径与“2/3次律”相近。在此基础上经验拟合出了适用于该测试地区C、D和E—F类大气稳定度条件下的烟气抬升高度计算式。