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An exact null controllability of stochastic singular systems

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Science China(Information Sciences) 2021年第7期64卷 247-249页

作者： Zhaoqiang GE xiaochi GE School of Mathematics and Statistics Xi'an Jiaotong University Cass Business School City University of London

Dear editor,The stochastic singular system is also called the stochastic differential algebraic system, stochastic descriptor system, generalized stochastic system, and stochastic degenerate system (e.g.,[1–4]). This type of system is found in numerous fields of application, which include fluid dynamics, the modeling of multi-body mechanisms, finance, inputoutput economics and the problem of protein folding.

关键词： stochastic system impulse solution exact null controllability Ito singular system stochastic Laplace transform

Spatial and Temporal Distribution of the Cryptospirifer Fauna(Middle Permian Brachiopods) in the Tethyan Realm and Its Paleogeographic Implications

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Acta Geologica Sinica(English Edition) 2008年第1期82卷 1-16页

作者： JIN xiaochi ZHAN Lipei Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China

The middle Permian Cryptospirifer fauna （brachiopod） has hitherto been found in more than 30 localities in the Yangtze Platform, South China. Examination of data from various localities shows that it occurs stratigraphically in three intervals in the range from the upper Kungurian to Wordian. In the Baoshan block in western Yunnan the fauna occurs in the basal part of the Daaozi Formation and is of possibly an early Wordian age. Outside China the Cryptospirifer fauna has been reported from central and northwest Iran and central Turkey, where the fauna may have an age around the Wordian／Capitanian boundary. Rapid global warming since the late Early Permian and possession of other suitable environmental factors such as proper substrate, clastic input and water depth enabled the Gondwana-derived Baoshan Block and related tectono-stratigraphic units in Iran and Turkey to host the Cryptospirifer fauna, a fauna evolved in the Yangtze Platform that is a type area of the Cathaysian province.

关键词： Cryptospirifer brachiopod Permian Tethys paleogeography

A novel unsupervised method for new word extraction

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Science China(Information Sciences) 2016年第9期59卷 11-21页

作者： Lili MEI Heyan HUANG xiaochi WEI Xianling MAO Beijing Engineering Research Center of High Volume Language Information Processing and Cloud Computing Applications Department of Computer Science and TechnologyBeijing Institute of Technology

New words could benefit many NLP tasks such as sentence chunking and sentiment analysis. However, automatic new word extraction is a challenging task because new words usually have no fixed language pattern, and even appear with the new meanings of existing words. To tackle these problems, this paper proposes a novel method to extract new words. It not only considers domain specificity, but also combines with multiple statistical language knowledge. First, we perform a filtering algorithm to obtain a candidate list of new words. Then, we employ the statistical language knowledge to extract the top ranked new words. Experimental results show that our proposed method is able to extract a large number of new words both in Chinese and English corpus, and notably outperforms the state-of-the-art methods. Moreover, we also demonstrate our method increases the accuracy of Chinese word segmentation by 10% on corpus containing new words.

关键词： new word extraction word segmentation domain specificity statistical language knowledge domain word extraction

Cesium-rubidium mineralization in Himalayan leucogranites

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Science China Earth Sciences 2023年第12期66卷 2827-2852页

作者： Fangyang HU xiaochi LIU Shaoxiong HE Jiamin WANG Fuyuan WU Key Laboratory of Mineral Resources Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 00029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

This paper presents a study of a newly discovered pollucite-lepidolite-albite granite(PLAG)in the Himalayan leucogranite belt,which marks the first occurrence of pollucite,a major cesium silicate mineral,in the Himalayan orogenic belt(China).The rock appears at the northern part of the Gyirong pluton,coexisting with the tourmaline-bearing two-mica granite(TMG).Primary rare-metal minerals include lepidolite(Li),spodumene(Li),pollucite(Cs),cassiterite(Sn),and microlite(Ta).Micas,mainly lithian muscovite to lepidolite,contain 4.07 wt.%Li_2O and 0.76 wt.%Rb_2O on *** average Li_2O content of the spodumene is 7.95 wt.%.Pollucite not only has an average Cs_2O content of 34 wt.%,but also has an elevated Rb_2O content of about 0.16 wt.%.Notably,this granite attains industrial grades for rare metals,specifically with Li_2O,Rb_2O,and Cs_2O contents of 0.49–1.19 wt.%,0.12–0.24 wt.%,and 0.69–2.33 wt.%,*** results of magmatic accessory cassiterite and monazite indicated that the PLAG was formed at 19–18 Ma,slightly later than the TMG(22–20 Ma)of the Gyirong ***,these two types of granites may form within the same magmatic system considering their pulsating intrusive contact,formation ages,and whole-rock and mineral chemical ***,the abundant presence of pollucite suggests that the PLAG experienced high degrees of magmatic *** comparison to the Pusila spodumene pegmatite in the Himalaya and the Yashan topaz-lepidolite granite in Jiangxi,South China,the Gyirong PLAG exhibits different whole-rock and mineral compositions,resulting from differences in source materials and fractionation ***,the difference in fluorine(F)content may determine the degree of rare-metal element *** discovery of Gyirong PLAG highlights multiple stages and types of rare-metal mineralization in the Himalayan leucogranite belt,which is controlled by the South Tibetan Detachment *** Cs-bearing geyserite deposit exp

关键词： Himalaya Pollucite Lepidolite Leucogranite Rare-metal elements

Highly fractionated granites:Recognition and research

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Science China Earth Sciences 2017年第7期60卷 1201-1219页

作者： WU FuYuan LIU xiaochi JI WeiQiang WANG JiaMin YANG Lei State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101 China College of Earth Sciences University of Chinese Academy of Sciences Beijing 100049 China

Granite is one of the most important components of the continental crust on our Earth; it thus has been an enduring studied subject in geology. According to present knowledge, granite shows a great deal of heterogeneity in terms of its texture,structure, mineral species and geochemical compositions at different scales from small dike to large batholith. However, the reasons for these variations are not well understood although numerous interpretations have been proposed. The key point of this debate is whether granitic magma can be effectively differentiated through fractional crystallization, and, if so, what kind of crystallization occurred during the magmatic evolution. Although granitic magma has high viscosity because of its elevated SiO2 content, we agree that fractional crystallization is effectively processed during its evolution based on the evidence from field investigation,mineral species and its chemical variations, and geochemical compositions. These data indicate that crystal settling by gravitation is not the only mechanism dominating granitic differentiation. On the contrary, flow segregation or dynamic sorting may be more important. Accordingly, granite can be divided into unfractionated, fractionated(including weakly fractionated and highly fractionated) and cumulated types, according to the differentiation degree. Highly fractionated granitic magmas are generally high in primary temperature or high with various volatiles during the later stage, which make the fractional crystallization much easier than the common granitic melts. In addition, effective magmatic differentiation can be also expected when the magma emplaced along a large scale of extensional structure. Highly fractionated granitic magma is easily contaminated by country rocks due to its relatively prolonged crystallization time. Thus, granites do not always reflect the characteristics of the source areas and the physical and chemical conditions of the primary magma. We proposed that h

关键词： Fractional crystallization Accumulation Highly fractionated granite Granitic magma Continental crustal evolution

Zircon Record of Ocean-Continent Subduction Transition Process of Dulan UHPM Belt, North Qaidam

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Journal of Earth Science 2015年第5期26卷 617-625页

作者： Jianzhou Yang xiaochi Liu Yuanbao Wu Yanling Sun Department of Earth Sciences China University of GeosciencesWuhan State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences

The North Qaidam UHPM（ultra-high pressure metamorphism） belt is a typical continental subduction-collision belt containing continental crust deep subduction metamorphic products and oceanic crust relics, And it is an ideal region to study the ocean-continent transition and exhumation mechanism of oceanic UHP rocks during continental deep subduction process. In this paper, we report integrated in situ U-Pb, Lu-Hf and O isotope analyses of zircons from a serpentinized harzburgite as well as U-Pb dating for zircons from a kyanite eclogite from the North Qaidam Dulan UHPM terrane, and use these data to discuss the ocean-continent transition and exhumation mechanisms of oceanic UHP rocks during continental deep subduction. The serpentinized harzburgite was dated at 448±9 Ma, consistent with 455±5 Ma age for the kyanite eclogite within analytical errors. Zircons from the serpentinized harzburgite have uniform 176Hf/177 Hf values ranging from 0.282 842 to 0.282 883 and εHf（t） values from 11.6 to 13.3. Zircon δ^18O values of the serpentinized harzburgite vary from 4.47‰ to 5.29‰, slightly lower than the value of 5.3‰±0.6‰ for the normal mantle zircon. These Hf-O isotopic features indicate that the protolith of the serpentinized harzburgite was derived from depleted-mantle source, and might have experienced high-temperature rock-water interaction. Therefore, the serpentinized harzburgite was possibly located in the lower part of an oceanic section. The serpentinized harzburgite and kyanite eclogite were both formed due to the subduction of oceanic crust. The UHP metamorphism occurred successively from the oceanic crust to continental crust rocks of the North Qaidam UHP terrane. Low-density serpentinized peridotite and continental rocks possibly have negative buoyancy and play a key effect on preservation and exhumation of high-density oceanic eclogite.

关键词： continental deep subduction ocean-continent transformation North Qaidam harzburgite eclogite

Lithologic Boundaries in Permian Post-glacial Sediments of the Gondwana-affinity Regions of China:Typical Sections,Age Range and Correlation

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Acta Geologica Sinica(English Edition) 2011年第2期85卷 373-386页

作者： JIN xiaochi HUANG Hao SHI Yukun ZHAN Lipei Institute of Geology Chinese Academy of Geological Sciences26 Baiwanzhuang Road Beijing 100037 China Department of Earth Sciences Nanjing Univeristy22 Hankou Road Nanjing Jiangsu 210093 China

In Southwest China, Gondwana-affinity Permo-Carboniferons deposits are known to occur in the Northern Himalayas, the Lhasa Block and the South Qiangtang Block, the Baoshan Block and the Tengchong Bock. The three-fold clastic successions, namely diamictite-pebbly mudstone-dark mudstone and shale are commonly interpreted as representing deposits of glacial-deglacial-postglacial periods in marine environments. Deposits, for example, the Dingjiazhai Formation in the Baoshan Block, the Kongshuhe Formation in the Tengchong Block, the Yongzhu Group and the Poindo Group in the Lhasa Block, are all succeeded by carbonate deposits. This marks a significant change from post-glacial clastic environment to a carbonate environment. Available paleontological data show that the change from post-glacial clastic environment to carbonate environment took place in the Baoshan, Tengchong and Lhasa Block at the beginning of the Artinskian. The carbonate environment in the Baoshan Block was spoiled by the eruption of the Woniusi Basalts, and in the Xainza area of the Lhasa Block was shortly replaced by clastic environment until the Kungurian. In the northern Himalayas limestones began to occur in the Late Permian in a fluctuating manner.

关键词： Permian Gondwana-affinity post-glacial Yunnan Tibet

Selective immobilization of Pb(Ⅱ)by biogenic whewellite and its mechanism

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Journal of Environmental Sciences 2024年第3期137卷 664-676页

作者： Xingxing Wang Kaiyan Ren Kairui Jiao Wenjun Nie xiaochi an Bin Lian College of Life Sciences College of Marine Science and EngineeringNanjing Normal UniversityNanjing 210023China

The development of bio-adsorbents with highly selective immobilization properties for specific heavy metals is a great challenge,but has important application *** whewellite(BW)with high selectivity for Pb(Ⅱ)was synthesized by mineral microbial *** selective immobilization properties and mechanism of BW for Pb(Ⅱ)were analyzed by combining mineral characterization technology and batch adsorption research *** results indicated that BW can efficiently and selectively immobilize Pb(Ⅱ)in single or composite heavy metal adsorption solutions,and the immobilized Pb(Ⅱ)is difficult to *** undergoes monolayer adsorption on Pb(Ⅱ),Qmax≈1073.17 mg/*** immobilization of Pb(Ⅱ)by BW is a physico-chemical adsorption process with spontaneous heat absorption and an accompanying increase in *** addition,the sequestration of Pb(Ⅱ)by BW remains around 756.99 mg/g even at p H=*** excellent selective immobilization properties of BW for Pb(Ⅱ)are closely related to its smaller Ksp,electrostatic repulsion effect,organic-inorganic composite structure,acid resistance and the formation of Pb(Ⅱ)*** study provides beneficial information about the recycling of lead in acidic lead-containing wastewater and composite heavy metal contaminated water bodies.

关键词： Aspergillus niger Biogenic whewellite Pb(Ⅱ) Selective adsorption Immobilization mechanism

High-Order Characteristic Modes Suppression for Cross-Band Decoupling in Shared-Aperture Antenna Array

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Chinese Journal of Electronics 2022年第6期31卷 1121-1128页

作者： LU xiaochi CHEN Yikai SHEN Tongsheng GUO Shaojun ZOU Chunrong YANG Shiwen School of Electronic Science and Engineering University of Electronic Science and Technology of China National Innovation Institute of Defense Technology Academy of Military Sciences PLA China

In dual-band shared-aperture base station antennas, the secondary radiation(SR) field caused by cross-band couplings always leads to radiation pattern distortion. In this work, the SR field caused by the coupling is attributed to the excitation of the target highorder modes from the perspective of the characteristic mode. To effectively suppress the target modes, L-shaped slots are proposed to load the arms of the radiator and altering the current paths. As compared with conventional dipoles without L-shaped slots, the proposed antenna generates less SR field. Therefore, the radiation pattern of the high-band antennas keeps stable in a dual-band shared-aperture antenna array environment. Prototype of a dual-band antenna array consisting of the proposed lowband(LB) antenna and a 4 × 4 high-band(HB) antenna array is fabricated. Simulated and measured results show that the designed dual-band array operates at both 0.74–0.82 GHz and 3.30–3.80 GHz. The experimental results verify that the cross-band decoupling has been achieved with the high-order mode suppression.

关键词： slot antenna arrays cross-band couplings radiation pattern distortion L-shaped slots secondary radiation field target modes 4 × 4 high-band antenna array low-band antenna dual-band shared-aperture base station antennas dual-band shared-aperture antenna array environment antenna radiation patterns dual-band array SR field high-order mode suppression aperture antennas multifrequency antennas cross-band decoupling target high-order modes high-order characteristic modes suppression UHF antennas