多年冻土区路桥过渡段一种新结构的试验观测与分析

基于保护多年冻土的原则,通过对一般地区过渡段设置方法的改进,得到了一种用于青藏铁路清水河地区的新型式路桥过渡段的设置方法.通过对过渡段的沉降和热状况的现场监测,分析了过渡段沉降变形和热状况的变化规律,并对采用的设置方法所产生的实际效果进行了评价.     

Earthquake source nucleation as self organization process

The theory of an earthquake source nucleation is discussed. Based on the assumption that self organization of damage process takes place in the zone of an earthquake source nucleation the theory incorporates the damage rheology framework of Lyakhovsky et al. and the approach of phenomenology theory of second-order phase transition. Namely, the free energy governing the process of an earthquake source nucleation depends on two collective variables α and φ in addition to the strain tensor ε_ij. The variable α quantifies the fracture of the medium and the variable φ quantifies the interaction effect of cracks. The region Ω_S is associated with a potential source of an earthquake if the damage variable α exceeds the critical value α_cr⁽¹⁾ inside Ω_S. The important feature of a potential source is that interaction of fractures causes acceleration of damage process inside the region of potential source and the material should lose stability primarily in this region. Interaction of fractures results also in occurrence of a residual stress caused by nonuniformity of fracture density. The appearance and development of the potential source result in increase of intensity of damage process not only in the region of potential source but also in a certain neighborhood of the last. It is compatible with such observed effects as acceleration of seismic energy release and growth of correlation length of weak seismicity before large earthquake. Transition of potential source to the stage of avalanche-unstable fracturing is associated with instability generated by explosive increase of interaction of fractures when the damage variable α exceeds the second critical value α_cr⁽²⁾ inside Ω_S.     

季风转换对深圳地区呼吸系统疾病的影响及预测研究

深圳地处我国华南沿海季风敏感区,为探究季风等气象和污染要素对其呼吸系统疾病发病的影响和其预测相关就诊风险的可行性,本文利用当地2015-2016年呼吸系统疾病就诊人数资料及同期气象和污染物资料,并运用BP人工神经网络和LSTM网络构建呼吸系统疾病就诊人数预测模型。结果显示:每年九月份开始,冬季风的冷胁迫效应会使相关人群呼吸系统疾病发病人数波动式增加,直至次年冬季风向夏季风转换前的三月份发病人数达到峰值;而夏季风控制期间当地居民呼吸系统疾病发病人数呈波动式减少态势,比峰值期间减少35%;另外,该地不同呼吸系统疾病其主控因素也不相同;对比两种预测模型,总体上LSTM网络预报模型对深圳呼吸系统疾病风险预测准确率更高,可以满足健康气象预报服务业务需求。     

TBB资料揭示的亚澳季风区季节转换及亚洲夏季风建立的特征

发展了一个用于台风路径预报的初始场人造台风方案。该方案除包含对称台风环流外,也考虑了非对称风的作用。使用双向移动套网格模式作的试验预报结果表明,初始场中引入人造台风后能明显提高径预报的水平。     

Seasonal patterns of soil respiration in three types of communities along grass-desert shrub transition in Inner Mongolia,China

The seasonal dynamics of soil respiration in steppe (S. bungeana), desert shrub (A. ordosica), and shrub-perennial (A. ordosica + C. komarovii) communities were investigated during the growth season (May to October) in 2006; their environmental driving factors were also analyzed. In the three communities, soil respiration showed similar characteristics in their growth seasons, with peak respiration values in July and August owing to suitable temperature and soil moisture conditions during this period. Meanwhile, changes in soil respiration were greatly influenced by temperatures and surface soil moistures. Soil water content at a depth of 0 to 10 cm was identified as the key environmental factor affecting the variation in soil respiration in the steppe. In contrast, in desert shrub and shrub-perennial communities, the dynamics of soil respiration was significantly influenced by air temperature. Similarly, the various responses of soil respiration to environmental factors may be attributed to the different soil textures and distribution patterns of plant roots. In desert ecosystems, precipitation results in soil respiration pulses. Soil carbon dioxide (CO₂) effluxes greatly increased after rainfall rewetting in all of the ecosystems under study. However, the precipitation pulse effect differed across the ecosystem. We propose that this may be a result of a reverse effect from the soil texture.     

Quantifying barriers to decarbonization of the Russian economy: real options analysis of investment risks in low-carbon technologies

Russia has significant potential for reducing its carbon emissions. However, investment in new low-carbon technologies has significant risks. Ambiguous energy and climate policy in Russia, along with deterioration of the country's investment climate, create investment barriers that are well described in qualitative terms in the literature. This paper attempts to provide a quantitative analysis of these barriers. For this numerical experiment, we apply the RU-TIMES model. Using a real options methodology, we estimate the risk-adjusted cost of capital in the Russian energy sector (including energy production and consumption technologies represented in the TIMES framework) to be approximately 43% (including a risk-free interest rate) and demonstrate the high risk of investment into energy-efficient and low-carbon technologies. Any future low-carbon emissions pathway depends on the ability of the Russian government to reduce climate and energy policy uncertainties, and to reduce financial risks through improvements of the general investment climate.

Key policy insights

• The high cost of capital investment into Russian energy production and consumption may prevent the adoption of new energy-efficient and low-carbon technologies.

• These investment risks, if not addressed, will delay Russia's low-carbon transition for the coming decades.

• Adopting a clear and unambiguous long-term climate and energy policy is important to reduce these risks and alleviate some of the barriers to the new technologies.

• The first step could be ratification of the Paris Agreement and adoption of a long-term emission target for the period up to 2050.

     

边界层控制转捩研究的新结果——流场测量和流动显示

给出边界层转捩研究的一些结果,这些结果包括实验观察到一个Λ结构中会出现4～5个小旋涡;Λ结构（又称Λ涡）是完整的蝴蝶型结构的一部分。孤立波结构存在于Λ结构的中心。     

Convergence or divergence?: Status and prospects for US climate strategy

The objective of this paper is to assess recent developments and prospects for future changes in United States (US) climate strategy. In doing so, the paper explores some of the key factors that have shaped strategies and policies to date, distinguishing between factors related to institutional and governance structures, linkages between science and policy, energy technology and the role of interest groups. Against this background, the paper attempts to explore future development paths for US climate policy. More specifically, the paper assesses opportunities for policy changes compared to the preferences of the current administration, and the prospects for future linkages between US and international climate change strategies. In brief, the paper argues that substantial changes are unlikely to take place in the near to medium term, leaving open, however, the possibility of wide-ranging changes in domestic politics or major incidents that could facilitate a shift in the perceived need for near-term action.     

旱,涝年与海气相互作用

利用１９５１￣１９９１年５００ｈＰａ高度场和海温场以及１９８０￣１９９１年ＴＢＢ资料，采用合成分析方法研究了东亚季风区季节转换在旱、涝年的不同特征。发现旱、涝年海温场分布型的不同及其形成的海气相互作用的差异使得西太平洋副热带高压在涝年季节北进较平缓，其脊线位置稳定在２５°Ｎ左右，强度较强，从而导致夏季风雨带在江淮流域停滞，形成江淮洪涝。中还讨论了中南半岛对流和赤道干旱带的变化对江淮流域旱、涝的先     

Problems of regional population growth in Serbia

The paper considers regional differences in population growth in Serbia and highlights the contrast that has emerged between Kosovo and Metohia and the other regions of the country since World War Two. Due to continuing high fertility coupled with declining mortality, growth in Kosovo and Metohia has been three times greater than in Serbia Proper and five times greater than in Voivodina, regions which have been following closely the European demographic transition. Since the population in Kosovo and Metohia is overwhelmingly Albanian these divergent demographic trends are sharpening ethnic tension as the demographic weight of the Serbs decreases in the country as a whole. At the same time the dominance of the Albanians within the province may well contribute to the independence struggle. Since the maintenance of high fertility, with a relatively slow decline - even in comparison with Albania - could be linked with externalities, it is suggested that a solution might be found in more autonomous development for the province which might bring an increase in local responsibility for sustainable development and a decrease in the currently high level of demographic investment. This revised version was published online in July 2006 with corrections to the Cover Date.