Rock physics and seismic reflectivity parameterization and amplitude variation with offsets inversion in terms of total organic carbon indicator

Total organic carbon (TOC) prediction with elastic parameter inversions has been widely used in the identification and evaluation of source rocks. However, the elastic parameters used to predict TOC are not only determined by TOC but also depend on the other physical properties of source rocks. Besides, the TOC prediction with the elastic parameters inversion is an indirect method based on the statistical relationship obtained from well logs and experiment data. Therefore, we propose a rock physics model and define a TOC indicator mainly affected by TOC to predict TOC directly. The proposed rock physics model makes the equivalent elastic moduli of source rocks parameterized by the TOC indicator. Combining the equivalent elastic moduli of source rocks and Gray’s approximation leads to a novel linearized approximation of the P-wave reflection coefficient incorporating the TOC indicator. Model examples illustrate that the novel reflectivity approximation well agrees with the exact Zoeppritz equation until incident angles reach 40°. Convoluting the novel P-wave reflection approximation with seismic wavelets as the forward solver, an AVO inversion method based on the Bayesian theory is proposed to invert the TOC indicator with seismic data. The synthetic examples and field tests validate the feasibility and stability of the proposed AVO inversion approach. Using the inversion results of the TOC indicator, TOC is directly and accurately estimated in the target area.

资源错配的来源、 趋势与分解

改革开放以来我国的资源配置方式和效率已经有了明显改善,然而各类非市场因素造成的结构性资源错配仍旧长期存在,影响着企业生产率和居民生活水平的提高。我们认为在研究资源配置效率时,既要关注其静态的水平,也要关注其动态的变化;既要关注其整体的扭曲程度,也要关注由于不同因素造成的扭曲分解。本文在HsiehandKlenow(2009)资源错配模型的基础上,提出了分组方差分解法:从总错配系数中分解出了"组间方差"用于测算由某一因素造成的资源错配程度,实现了不同扭曲因素之间的跨期可比,为分析比较错配的来源及其变化趋势提供了标准化的方法。基于该方法,本文使用中国工业企业数据库,选取了文献中六个被广泛讨论的扭曲来源,即企业所有制、企业成立年限、企业规模、省份地区、城市等级、补贴政策,对1998—2013年资源错配的来源进行分解测算。研究发现:最近二十年我国资源错配的来源结构发生了较大变化,传统的由企业所有制、成立年限造成的错配目前已明显改善;与此同时,由于地区不平衡发展、中小企业融资约束等因素造成的扭曲显著上升,并直接导致2005年后资源配置效率的下降。特别是在2008年"四万亿"计划实施后,由于补贴等政策因素所造成的扭曲明显上升,导致了资源配置效率的进一步下降。本文的发现为我们全面认识中国资源错配的来源和趋势,深入推进并重点布局要素市场化改革等现实问题提供了新的思路和依据。

国内矛盾与贸易保护主义:基于推特文本的实证研究

已有经济学和政治学文献指出非贸易因素可能导致贸易保护主义,然而由于各国政治决策过程不透明、数据难以获取、民众对不同政策的反馈难以观测等原因,文献中对该机制的研究长期以来存在不足,尤其是缺乏可靠的量化实证研究作为支持。本文在运用机器学习方法对特朗普在社交平台“推特”上发布的30902条推文进行数据挖掘的基础上,以特朗普对华贸易保护主义言论及民意反馈为典型研究对象实证检验了美国国内矛盾对近年来美国贸易保护主义抬头的影响,为“国内矛盾论”理论假说提供了新的实证证据。研究发现,样本期内,民调反对率、股市恐慌指数等反映美国国内矛盾的非贸易因素对特朗普发表对华贸易保护主义言论具有显著影响;相反,贸易因素的影响并不显著。且在中美两国签订第一阶段经贸协议之后,美国国内矛盾对特朗普对华贸易保护主义言论的影响机制并未发生根本改变。研究还发现,特朗普在社交平台上发表对华强硬的言论能够获得更高的民意支持。本文的结论表明,当美国国内社会经济出现治理危机时,特朗普为了转移国内矛盾、博取选民支持,更倾向于发表强硬的对华贸易保护主义言论。一个直接的推论是受国内政治经济矛盾未来一段时期持续存在的影响,美国针对中国的贸易保护主义政策很可能会继续存在。因此,中国经济必须加快构建双循环新发展格局。

iVenomDB: A manually curated database for insect venom proteins

DearEditor,Venomous animals,such as snakes,insects(wasps,bees,ants,and some bugs),spiders,scorpions,and cone snails,use venom for predation and/or defense.Venom is mostly composed of proteinsand peptides.Because of their high potency and selectivity,venom components have been developed into valuable resources,such as research tools,bioinsecticides(Heep et al.,2019),and drug leads(Badawi,2021).The advent of high-throughput sequencing and mass spectrometry enabled exploration of venom components to new depths and at an unprecedented pace.To be useful to the scientific community,knowledge on these proteins must be stored in a retrievable manner,annotated,and curated.Currently,several databases are dedicated to venoms from a wide range of animals,such as Arachnoserver(Pineda et al.,2018),Conoserver(Kaas et al.,2012),and the Tox-Prot program within UniprotKB(Jungo et al.,2012).