Corona-like atmospheric escape from KBOs: II. The behavior of aerosols

In Levi and Podolak (Levi, A., Podolak, M. [in press] Icarus) we applied the theory of coronal expansion to gas escape from a small, cold, object such as those found in the Kuiper belt. Here we extend the theory to include aerosols that are lifted off the surface by the escaping gas. Aerosols carried by the gas but still gravitationally bound, tend to be lifted to a height above the surface that is dependent on the aerosol radius, so that in steady state the variation of aerosol radius with height is well-defined. We develop an extension of Parker’s coronal flow theory to include the effect of aerosols carried along by the gas and use this to estimate the optical depth of such an atmosphere. For KBOs with CO evaporation from the surface and with radii in the range 245-334 km, line-of-site optical depths through the atmosphere can exceed one at heights of a few hundred kilometers above the surface. Such aerosol layers should be observable, and might be used to infer the flow proprieties of the escaping gas.     

转换波和非转换波与射线参数p的关系

本文对Aki固体-固体分界面的反射和透射公式进行适当变换,使之成为一组适合不同坐标系下,固体、液体、气体和真空之间所有可能形成的分界面上,入射P、SV和SH波所形成的反射和透射公式,从而把不同边界条件的反射和透射方程统一起来,并且阐明了转换波和非转换波动力学特征的差异.指出:在不同弹性介质分界面上入射平面弹性波,转换波的反射系数和透射系数是射线参数p的奇函数;非转换波的反射系数和透射系数是射线参数p的偶函数.根据奇函数和偶函数的性质可见:垂直入射时不存在转换波.同时也为简化Zoeppricz方程,开展AVO分析打开新思路.     

Land use classification from multitemporal Landsat imagery using the Yearly Land Cover Dynamics (YLCD) method

Several previous studies have shown that the inclusion of the LST (Land Surface Temperature) parameter to a NDVI (Normalized Difference Vegetation Index) based classification procedure is beneficial to classification accuracy. In this work, the Yearly Land Cover Dynamics (YLCD) approach, which is based on annual behavior of LST and NDVI, has been used to classify an agricultural area into crop types. To this end, a time series of Landsat-5 images for year 2009 of the Barrax (Spain) area has been processed: georeferenciation, destriping and atmospheric correction have been carried out to estimate NDVI and LST time series for year 2009, from which YLCD parameters were estimated. Then, a maximum likelihood classification was carried out on these parameters based on a training dataset obtained from a crop census. This classification has an accuracy of 87% (kappa = 0.85) when crops are subdivided in irrigated and non-irrigated fields, and when cereal crops are aggregated in a single crop, and performs better than a similar classification from Landsat bands only. These results show that a good crop differentiation can be obtained although detailed crop separation may be difficult between similar crops (barley, wheat and oat) due to similar annual NDVI and LST behavior. Therefore, the YLCD approach is suited for vegetation classification at local scale. As regards the assessment of the YLCD approach for classification at regional and global scale, it will be carried out in a further study.     

地震体波的动力学辐射理论

本文利用弹性介质的动力学关系建立了地震体波辐射动力学理论，并给出了地震远场体波位移的多级展开式，然后，对零级辐射及一级辐射做了重点讨论，作为地震辐射场源的内外激发源具有明显的物理意义。     

Observed dynamic soil–structure interaction in scale testing of offshore wind turbine foundations

Monopile foundations have been commonly used to support offshore wind turbine generators (WTGs), but this type of foundation encounters economic and technical limitations for larger WTGs in water depths exceeding 30 m. Offshore wind farm projects are increasingly turning to alternative multipod foundations (for example tetrapod, jacket and tripods) supported on shallow foundations to reduce the environmental effects of piling noise. However the characteristics of these foundations under dynamic loading or long term cyclic wind turbine loading are not fully understood. This paper summarises the results from a series of small scaled tests (1:100, 1:150 and 1:200) of a complete National Renewable Energy Laboratory (NREL) wind turbine model on three types of foundations: monopiles, symmetric tetrapod and asymmetric tripod. The test bed used consists of either kaolin clay or sand and up to 1.4 million loading cycles were applied. The results showed that the multipod foundations (symmetric or asymmetric) exhibit two closely spaced natural frequencies corresponding to the rocking modes of vibration in two principle axes. Furthermore, the corresponding two spectral peaks change with repeated cycles of loading and they converge for symmetric tetrapods but not for asymmetric tripods. From the fatigue design point of view, the two spectral peaks for multipod foundations broaden the range of frequencies that can be excited by the broadband nature of the environmental loading (wind and wave) thereby impacting the extent of motions. Thus the system lifespan (number of cycles to failure) may effectively increase for symmetric foundations as the two peaks will tend to converge. However, for asymmetric foundations the system life may continue to be affected adversely as the two peaks will not converge. In this sense, designers should prefer symmetric foundations to asymmetric foundations.     

Factors driving the seasonal distribution of planktonic and epiphytic ciliates in a eutrophicated Mediterranean Lagoon

We studied the distribution of planktonic and epiphytic ciliates coupled with environmental factors and microalgae abundance at five stations in Ghar El Melh Lagoon (Tunisia). Planktonic ciliates were monitored for a year and epiphytic ciliates were sampled during summer 2011 in concordance with the proliferation of the seagrass Ruppia cirrhosa. Ciliate assemblage was largely dominated by Spirotrichea followed respectively by Tintinnida of and Strombidiida. No significant difference was found in the distribution of ciliate species among the stations. Redundancy analysis indicates that abiotic factors (temperature and nutriments) have a significant effect on the dynamics of certain ciliates. For epiphytic ciliates, 4 species were identified: Tintinnopsis campanula, Aspidisca sp., Strombidium acutum and Amphorides amphora. Based on PERMANOVA analyses, ciliates exhibit significant correlations among months and stations. According to ACP, epiphyte distribution follows roughly those of R. cirrhosa and pH. Significant correlations were found between harmful dinoflagellates and both planktonic and epiphytic ciliates.     

2007年宁洱6.4级地震研究

根据云南宁洱地区地质构造、 历史强震资料、 云南监测中心区域台及现场流动台数字化观测台网测定的2007年宁洱6.4级地震序列资料及1970年以来宁洱地区6级地震序列等, 深入分析研究了宁洱地区中强地震活动规律、 宁洱6.4级地震的余震时空展布以及参数变化等特征, 并利用2007年宁洱6.4级地震地震现场数字化观测流动台测定的余震波资料研究了该序列地震波动力学特征。 研究结果认为, 宁洱6级地震活动在空间上具有较高的原地重复性, 在时间上具有强弱交替活动的韵律; 2007年6月3日宁洱6.4级地震的余震展布方向与穿过震区NW向宁洱断裂的走向大致一致, 宁洱6.4级地震可能是由无量山断裂活动构造加剧所引起;根据2007年6月3日宁洱6.4级地震序列及历次宁洱6级地震序列时序发展特征分析研究得出, 宁洱6.4级地震序列能量主要集中在震后3天内释放, 4.9级以上余震发生在主震当天, 地震序列早期参数和3.0级以上余震的垂直方向P波最大振幅与S波最大振幅非线性关系等显示, 宁洱6.4级地震序列具有较明显的主-余震型特征。     

Impact of Estuarine Outflow on Coastal Upwelling

A two-dimensional numerical model is developed facilitating the locationwise study of coastal upwelling. The coastal rigid boundary in the model is replaced with an open boundary to understand the dynamical response of the coastal ocean in the presence of an estuary. The model is applied to the east coast of India in a plane perpendicular to the coast of Kakinada where the Godavari river joins the Bay of Bengal. The model is driven, starting from a state of rest, by the combined effect of the wind stress forcing and the freshwater discharge from the estuary. Two numerical experiments were conducted to study the effect of the variation in the freshwater discharge on upwelling. It is found that the freshwater discharge from the Godavari estuary suppresses the upwelling off Kakinada.     

Individual transferable quotas versus auctioned seasonal quotas: An experimental investigation

Fishery policies have largely developed in response to revealed problems with existing policy instruments. The last major innovation is the introduction of individual transferable quotas, ITQs. Experience thus far is promising. However, if history repeats itself, it is pertinent to start exploring further improvements. Among other things, concerns may be raised about the efficiency of ITQs, financial risks to owners of quotas and fishing vessels, and problems with fairness and collection of resource rent. These issues are studied with a laboratory experiment. Different from previous experiments it allows for trade of both quotas and vessels. In addition, the experiment tests an alternative institutional arrangement, namely auctioned seasonal quotas, ASQs. Neither of the two systems turns out to be as perfect as economic theory predicts. While the two systems are similar in some respects, the ASQ system allows for taxation of resource rent, and surprisingly, it may be the system with the lowest financial risk for fishing firms.     

Precipitation,dynamical intermittency,and sporadic randomness

While rainfall intermittency is a dynamical phenomenon, little progress has been made in the literature on the link between rainfall intermittency and atmospheric dynamics. We present the basic dynamical models of intermittency that are phenomenologically most similar to rainfall: Pomeau–Manneville Type-III and On–Off. We then illustrate each type with both a 1-D iterative map and a corresponding stochastic process stressing the appearance of these dynamics in high-dimensional (stochastic) systems as opposed to low-dimensional chaotic systems. We show that the pdf of rainfall intensities, the pdf of “laminar phases” (periods of zero rainfall intensity), and the spectrum of the rainfall series all have power-law behavior that is broadly consistent with intermittency in the classic types. Using a seasonal analysis, we find that summer convective rainfall at daily and sub-daily scales seems consistent with features of Type-III intermittency. The correspondence with Type-III intermittency and a preliminary entropic analysis further suggest that rainfall may be an example of sporadic randomness, blending deterministic and stochastic components.