Two energy balance closure approaches： applications and comparisons over an oasis-desert ecotone

Studies of energy balance that rely on eddy covariance（EC） are always challenged by energy balance closure, which is mainly caused by the underestimations of latent heat flux（LE） and sensible heat flux（Hs）. The Bowen ratio（BR） and energy balance residual（ER） approaches are two widely-used methods to correct the LE. A comprehensive comparison of those two approaches in different land-use types is essential to accurately correcting the LE and thus improving the EC experiments. In this study, two energy balance approaches（i.e., BR and ER） were compared to correct the LE measured at six EC sites（i.e., three vegetated, one mixed and two non-vegetated sites） in an oasis-desert ecotone of the Heihe River Basin, China. The influences of meteorological factors on those two approaches were also quantitatively assessed. Our results demonstrated that the average energy closure ratio（（LE＋Hs）/（Rn–Gs）; where Rn is the surface net radiation and Gs is the surface soil heat flux） was approximately close to 1.0 at wetland, maize and village sites, but far from 1.0 at orchard, Gobi and desert sites, indicating a significant energy imbalance at those three latter sites. After the corrections of BR and ER approaches that took into account of soil heat storage, the corrected LE was considerably larger than the EC-measured LE at five of six EC sites with an exception at Gobi site. The BR and ER approaches yielded approximately similar corrected LE at vegetated and mixed sites, but they generated dissimilar results at non-vegetated sites, especially at non-vegetated sites with low relative humidity, strong wind, and large surface-air temperature difference. Our findings provide insight into the applicability of BR and ER approaches to correcting EC-based LE measurements in different land-use types. We recommend that the BR-corrected and ER-corrected LE could be seriously reconsidered as validation references in dry and windy areas.

RESEARCH ON MATRIX CRACK EVOLUTION OF CROSS-PLY CERAMIC MATRIX COMPOSITE

The matrix crack evolution of cross-ply ceramic matrix composites under uniaxial tensile loading is investigated using the energy balance method.Under tensile loading,the cross-ply ceramic matrix composites have five damage modes.The cracking mode 3 contains transverse cracking,matrix cracking and fiber/matrix interface debonding.The cracking mode 5 only contains matrix cracking and fiber/matrix interface debonding.The cracking stress of modes 3 and 5 appearing between existing transverse cracks is determined.And the multiple matrix crack evolution of mode 3 is determined.The effects of ply thickness,fiber volume fraction,interface shear stress and interface debonding energy on the cracking stress and matrix crack evolution are analyzed.Results indicate that the cracking mode 3 is more likely to appear between transverse cracks for the SiC/CAS material.

Method for identifying effective carbonate source rocks:a case study from Middle-Upper Ordovician in Tarim Basin,China

Hydrocarbon expulsion occurs only when pore fluid pressure due to hydrocarbon generation in source rock exceeds the force against migration in the adjacent carrier beds.Taking the Middle-Upper Ordovician carbonate source rock of Tarim Basin in China as an example,this paper proposes a method that identifies effective carbonate source rock based on the principles of mass balance.Data from the Well YW2 indicate that the Middle Ordovician Yijianfang Formation contains effective carbonate source rocks with low present-day TOC.Geological and geochemical analysis suggests that the hydrocarbons in the carbonate interval are likely self-generated and retained.Regular steranes from GC-MS analysis of oil extracts in this interval display similar features to those of the crude oil samples in Tabei area,indicating that the crude oil probably was migrated from the effective source rocks.By applying to other wells in the basin,the identified effective carbonate source rocks and non-source rock carbonates can be effectively identified and consistent with the actual exploration results,validating the method.Considering the contribution from the identified effective source rocks with low present-day TOC(TOC_(pd))is considered,the long-standing puzzle between the proved 3 P oil reserves and estimated resources in the basin can be reasonably explained.

China＇s Sovereign Balance Sheet and Its Risk Assessment

Using available data and necessary estimations, this paper provides a tentative picture of the balance sheet of China＇s sovereign account between 2000 and 2010. The main findings indicate that the net worth of China＇s sovereign assets had been positive and increasing during the period under review. This implies that the Chinese government has sufficient sovereign assets to cover its sovereign liabilities, therefore the likelihood of a sovereign debt crisis in China is extremely low in the near term. Moreover, although China＇s leverage ratio （total liabilities/GDP） is far lower compared to advanced economies, it seems higher than that of other major emerging economies such as Brazil, Russia, and India （BRIC）. In fact, the leverage ratio has been increasing rapidly over recent years and requires special attention. In particular, according to sector-specific analysis, high corporate liability ratios （percentage to GDP） constitute a major concern of China＇s national balance sheet. In 2010, this liability ratio exceeded l OO percent, which exceeds the 90 percent level observed in OECD countries. Lastly, this paper concludes that a sustainable economic growth and structural transformation of growth model are the fundamental means to taming China＇s balance sheet risks.

Characteristics and origin of low-organicmatter carbonate source rocks in the Middle-Upper Ordovician, Tarim Basin, northwestern China

The continually-discovered large volumes of marine hydrocarbons indicate a huge exploration potential within the carbonate rocks of Ordovician in the Tarim Basin,northwestern China.The Middle-Upper Ordovician(O2+3)carbonate source rocks are at a highly mature stage.These rocks presently contain a low amount of total organic carbon(TOC_(pd)≤0.5%)(TOC_(pd) means the present-day TOC).A mass balance approach is used to identify the source rocks that have expelled hydrocarbons.The characteristics and origin of hydrocarbon expulsion from low-TOC_(pd) source rocks are studied,which are significant for oil exploration in the basin.The results showed that a low-TOC_(pd) O2+3 source rock having expelled hydrocarbons was type I and had a very narrow oil window.With a high rock maturity and a high original TOC(TOCo)value exceeding 1%,nearly 80%of the generated hydrocarbons were expelled.The content of gammacerane and C28 steranes in the oil and source rock extracts were relatively lean,with a V-shaped distribution of regular steranes,suggesting a possible genetic relation between the low-TOC_(pd) source rocks and the marine oil in the Tabei area.Hydrogenrich planktonic algae or acritarchs were the main hydrocarbon parent materials,distributed in the subsiding platform-slope facies.Organic matter was preserved under reducing conditions,and source rocks were formed with a favorable kerogen type and a moderate hydrocarbon generation potential.This study illustrates the hydrocarbon expulsion of low TOC_(pd) source rocks in northern Tarim Basin,which is greatly significant for analyzing the genesis of marine crude oil in Tarim Basin,and evaluating the distribution of marine source rocks.This research method is theoretically significant for oil and gas exploration in the same type of highlymature carbonate paleobasins.

Does Practice Always Make Perfect?——random notes on the need for a judicious balance between assimilative and systematic approaches in English language teaching

本文探讨外语院校英语教学中的一些问题。 英语专业有些学生基础不扎实,笔头表达能力很弱。针对这种情况,文章着重谈了三个问题: 1.语法问题:用正确的方法学习语法,辨明英语和汉语的差异有助于克服母语干扰,学好英语。 2.词典问题:在强调通过语境学习语言的同时,应当注意培养学生使用工具书的能力。查阅词典能使学生集中地研究、掌握词义和用法,可以补阅读之不足。 3.精读和泛读问题:精读和泛读各有其作用,应当二者并举,互相结合。 结论是英语教学要“两条腿走路”:一方面努力创造良好的语言环境,让学生通过自然熏陶的方式学习英语;同时也要注意引导学生有意识地研究语言和语言规律。

DIFFICULTIES CONFRONTED BY ICSID TRIBUNALS IN DECIDING INTERNATIONAL INVESTMENT CORRUPTION CASES AND POSSIBLE SOLUTIONS

The issue of corruption has attracted increasing attention in the study and practice of international investment law during recent years.After taking prudent consideration of the corruption defense invoked by the host states in some international investment arbitration cases involved with corruption,International Center for Settlement of Investment Disputes(ICSID)tribunals accordingly determined the final awards.However,some parts of the arbitral jurisprudence aroused strong criticism,especially with regard to the ICSID tribunals’reasoning that arbitrators have no jurisdiction over corruption-tainted international investments.The ICSID tribunals are legitimately supposed to exercise their jurisdiction and are lawfully obliged to probe into the nature of corrupt activities.The tribunals are strongly expected to adopt a balanced approach in deciding the merits and fairly weighing the obligations,rights,and interests of both disputing parties.It is preferable to strengthen the collaborative interaction between ICSID proceedings and domestic anti-corruption enforcement mechanisms when it comes to combating corrupt international investment activities.Existing international treaties(or specific treaty provisions)on combating corruption in international business transactions and calling for international cooperation,alongside domestic anti-corruption enforcement legislation,have actually laid solid legal foundations for the establishment of such an anti-corruption coordinative mechanism between ICSID and domestic corruption regulatory authorities on the global level.