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Numerical modeling of fracture propagation of supercritical CO_(2)compound fracturing

Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2607-2628页

作者： Hao Chen Yong kang Wanchun Jin Changhai Li Can Cai School of Mechanical Engineering Southwest Petroleum UniversityChengdu610500China Laboratory of High-pressure Jet Theory and Application Technology Southwest Petroleum UniversityChengdu610500China Hubei Key Laboratory of Waterjet Theory and New Technology Wuhan UniversityWuhan430072China Sinopec International Petroleum Exploration and Production Corporation Beijing 100029China

The exploitation of shale gas is promising due to depletion of the conventional energy and intensification of the greenhouse *** this paper,we proposed a heat-fluid-solid coupling damage model of supercritical CO_(2)(SC-CO_(2))compound fracturing which is expected to be an efficient and environmentally friendly way to develop shale *** coupling model is solved by the finite element method,and the results are in good agreement with the analytical solutions and fracturing *** on this model,the fracture propagation characteristics at the two stages of compound fracturing are studied and the influence of pressurization rate,in situ stress,bedding angle,and other factors are *** results show that at the SC-CO_(2)fracturing stage,a lower pressurization rate is conducive to formation of the branches around main fractures,while a higher pressurization rate inhibits formation of the branches around main fractures and promotes formation of the main *** bedding and in situ stress play a dominant role in the fracture *** the in situ stress ratio(sx/sy)is 1,the presence of bedding can reduce the initiation pressure and failure ***,it will cause the fracture to propagate along the bedding direction,reducing the fracture *** rocks without bedding,hydraulic fracturing has the lengthening and widening effects for SC-CO_(2)induced *** shale,fractures induced at the hydraulic fracturing stage are more likely to be dominated by in situ stresses and have a shorter reorientation ***,fracture branches propagating along the maximum principal stress direction may be generated around the main fractures induced by SC-CO_(2)at the hydraulic fracturing *** the branches converge with the main fractures,fracture zones are easily formed,and thus the fracture complexity and damage area can be significantly *** results are instructive for the design and application of SC-CO_(2

关键词： Compound fracturing Fracture propagation Finite element method Damage evolution

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Alterations of soil aggregates and intra-aggregate organic carbon fractions after soil conversion from paddy soils to upland soils:Distribution,mineralization and driving mechanism

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Pedosphere 2024年第1期34卷 121-135页

作者： Longfei kang Jiamei WU Chunfeng ZHANG Baoguo ZHU Guixin CHU College of Life Science Shaoxing UniversityShaoxing 312000China The Key Laboratory of Oasis Eco-agriculture Xinjiang Production and Construction Group/Department of Resources and Environmental SciencesAgronomy CollegeShihezi UniversityShihezi 832000China Hunan Institute of Agricultural Environment and Ecology Changsha 410000China Jiamusi Branch Heilongjiang Academy of Agricultural SciencesJiamusi 154007China

Investigating the impacts of soil conversion on soil organic carbon(OC) content and its fractions within soil aggregates is essential for defining better strategies to improve soil structure and OC sequestration in terrestrial ecosystems. However, the consequences of soil conversion from paddy soil to upland soil for soil aggregates and intra-aggregate OC pools are poorly understood. Therefore, the objective of this study was to quantify the effects of soil conversion on soil aggregate and intra-aggregate OC pool distributions. Four typical rice-producing areas were chosen in North and South China, paired soil samples(upland soil converted from paddy soil more than ten years ago vs. adjacent paddy soil) were collected(0–20 cm) with three replicates in each area. A set of core parameters(OC preservation capacity, aggregate carbon(C) turnover, and biological activity index) were evaluated to assess the responses of intra-aggregate OC turnover to soil conversion. Results showed that soil conversion from paddy soil to upland soil significantly improved the formation of macro-aggregates and increased aggregate stability. It also notably decreased soil intra-aggregate OC pools, including easily oxidized OCa(EOCa), particulate OCa(POCa), and mineral-bound(MOCa) OC, and the sensitivity of aggregate-associated OC pools to soil conversion followed the order: EOCa(average reduction of 21.1%) > MOCa(average reduction of 15.4%) > POCa(average reduction of 14.8%). The potentially mineralizable C(C_(0)) was significantly higher in upland soil than in paddy soil, but the corresponding decay constant(k) was lower in upland soil than in paddy soil. Random forest model and partial correlation analysis showed that EOCa and pH were the important nutrient and physicochemical factors impacting k of C mineralization in paddy soil,while MOCa and C-related enzyme(β-D-cellobiohydrolase) were identified as the key factors in upland soil. In conclusion, this study evidenced that soil conversion

关键词： decay constant easily oxidized organic C macro-aggregate meso-aggregate micro-aggregate mineral-bound organic C particulate organic C potentially mineralizable C

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Transfer matrix method for free and forced vibrations of multi-level functionally graded material stepped beams with different boundary conditions

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Applied Mathematics and Mechanics(English Edition) 2024年第6期45卷 983-1000页

作者： Xiaoyang SU Tong HU Wei ZHANG Houjun kang Yunyue CONG Quan YUAN School of Civil Engineering and Architecture Guangxi UniversityNanning 530004China Scientific Research Center of Engineering Mechanics Guangxi UniversityNanning 530004China State Key Laboratory of Featured Metal Materials and Life-Cycle Safety for Composite Structures Guangxi UniversityNanning 530004China

Functionally graded materials(FGMs)are a novel class of composite materials that have attracted significant attention in the field of engineering due to their unique mechanical *** study aims to explore the dynamic behaviors of an FGM stepped beam with different boundary conditions based on an efficient solving *** the assumptions of the Euler-Bernoulli beam theory,the governing differential equations of an individual FGM beam are derived with Hamilton’s principle and decoupled via the separation-of-variable ***,the free and forced vibrations of the FGM stepped beam are solved with the transfer matrix method(TMM).Two models,i.e.,a three-level FGM stepped beam and a five-level FGM stepped beam,are considered,and their natural frequencies and mode shapes are *** demonstrate the validity of the method in this paper,the simulation results by ABAQUS are also *** this basis,the detailed parametric analyses on the frequencies and dynamic responses of the three-level FGM stepped beam are carried *** results show the accuracy and efficiency of the TMM.

关键词： transfer matrix method(TMM) free vibration forced vibration functionally graded material(FGM) stepped beam

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Enhancing leaching efficiency of ion adsorption rare earths by ameliorating mass transfer effect of rare earth ions by applying an electric field

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Journal of Rare Earths 2024年第1期42卷 172-180,I0006页

作者： Lingbo Zhou Jie Yang Shijie kang Xiaojun Wang hongdong Yu Yinhua Wan Rare Earth Institute University of Science and Technology of ChinaHefei230000China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou341000China Jiangxi Institute of Rare Earths Chinese Academy of SciencesGanzhou341000China School of Resources and Environment Engineering Jiangxi University of Science and TechnologyGanzhou341000China

Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare *** this study,2 wt%MgSO_(4)solution was used for the indoor simulated column leaching experiment on rare earth samples and an electric field was applied at both ends of the *** the effects of different intensities,initial application time and duration of the electric field on the rare earth leaching system and its mechanism were *** results show that compared with the single MgSO_(4)solution leaching,applying an electric field with a strength of 6 V/cm can save the leaching time of 30 min and increase the flow velocity of the rare earth leachate by 26.98%.Under the optimal conditions of applying an electric field with a strength of 6 V/cm for 20 min to the leaching system after10 min of the rare earth leachate flowing out,the leaching efficiency of sample increases from 81.20% to 86.05% with the increase of 4.85%.The mechanism analysis shows that when a direct current electric field is applied to the rare earth leaching system,rare earth ions rapidly change from disorderly movement with the seepage into faster and directional *** addition,the seepage of the leaching solution is also improved due to the increase of the cross-sectional area of the seepage channel,the polarized water molecules migrate directionally by force from the negative pole,and the movement of the hydrogen is generated by the electrolytic *** impo rtantly,based on the principle of in-situ leaching process,the layout of injection holes and deflector holes in this process provides a natural site for the electrode layout of the electric *** the simple equipme nt and the ope ration,the rare earth leaching process with the applied electric field has high feasibility in industrial application.

关键词： Ion adsorption rare earths Leaching system Electric field Mass transfer process Seepage

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Experimental study on secondary air mixing along the bed height in a circulating fluidized bed with a multitracer-gas method

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Chinese Journal of Chemical Engineering 2024年第6期70卷 54-62页

作者： Qingyu Zhang Leming Cheng Kun Li Qixun kang Qiang Guo Chaogang Wu Institute for Thermal Power Engineering State Key Laboratory of Clean Energy UtilizationZhejiang UniversityHangzhou 310027China Dongfang Boiler Group Co.Ltd. Zigong 643001China

A multitracer-gas method was proposed to study the secondary air(SA)mixing along the bed height in a circulating fluidized bed(CFB)using carbon monoxide(CO),oxygen(O_(2)),and carbon dioxide(CO_(2))as tracer *** were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 *** effects of superficial velocity,SA ratio,bed inventory,and particle diameter on the SA mixing were *** results indicate that there are some differences in the measurement results obtained using different tracer gases,wherein the deviation between CO and CO_(2) ranges from 42%to 66%and that between O_(2) and CO_(2) ranges from 45%to 71%in the lower part of the fluidized ***,these differences became less pronounced as the bed height ***,the high solid concentration and fine particle diameter in the CFB may weaken the *** measurement results of different tracer gases show the same trends under the variation of operating *** superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the *** effect of bed inventory on SA mixing is not monotonic.

关键词： Circulating fluidized bed Secondary air injection Gas mixing Multitracer-gas method

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Broadband Dual-Input Doherty Power Amplifier Design Based on a Simple Adaptive Power Dividing Ratio Function

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China Communications 2024年第5期21卷 97-112页

作者： Dai Zhijiang Zhong kang Li Mingyu Pang Jingzhou Jin Yi School of Microelectronics and Communication Engineering Chongqing UniversityChongqing 400044China Xi’an Branch of China Academy of Space Technology Xi’an 710100China

In this paper,a simple adaptive power dividing function for the design of a dual-input Doherty power amplifier(DPA)is *** the presented approaches,the signal separation function(SSF)at different frequency points can be characterized by a *** in the practical test,the coefficients of SSF can be determined by measuring a small number of data points of input *** as other dualinput DPAs,the proposed approach can also achieve high output power and back-off efficiency in a broadband operation band by adjusting the power distribution ratio ***,a 1.5-2.5 GHz highefficiency dual-input Doherty power amplifier is implemented according to this *** test results show that the peak power is 48.6-49.7d Bm,and the 6-d B back-off efficiency is 51.0-67.0%,and the saturation efficiency is 52.4-74.6%.The digital predistortion correction is carried out at the frequency points of 1.8/2.1GHz,and the adjacent channel power ratio is lower than-54.5d *** and experiment results can verify the effectiveness and correctness of the proposed method.

关键词： broadband doherty power amplifier dualinput efficiency enhancement load modulation

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On-surface synthesis and characterization of polyynic carbon chains

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National Science Review 2024年第3期11卷 192-199页

作者： Wenze Gao Wei Zheng Luye Sun Faming kang Zheng Zhou Wei Xu Interdisciplinary Materials Research Center School of Materials Science and Engineering Tongji University

Carbyne, an elusive sp-hybridized linear carbon allotrope, has fascinated chemists and physicists for decades. Due to its high chemical reactivity and extreme instability, carbyne was much less explored in contrast to the sp2-hybridized carbon allotropes such as graphene. Herein, we report the on-surface synthesis of polyynic carbon chains by demetallization of organometallic polyynes on the Au（111） surface;the longest one observed consists of ～60 alkyne units（120 carbon atoms）. The polyynic structure of carbon chains with alternating triple and single bonds was unambiguously revealed by bond-resolved atomic force microscopy. Moreover, an atomically precise polyyne, C14, was successfully produced via tip-induced dehalogenation and ring-opening of the decachloroanthracene molecule(C14Cl10) on a bilayer NaCl/Au（111） surface at 4.7 K, and a band gap of 5.8 eV was measured by scanning tunnelling spectroscopy,in a good agreement with the theoretical HOMO–LUMO gap（5.48 eV）.

关键词： polyyne scanning probe microscopy carbon allotrope on-surface synthesis organometallic polyyne

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Attitude control of multi-spacecraft systems on SO(3)with stochastic links failure

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Chinese Journal of Aeronautics 2024年第3期37卷 320-331页

作者： kang Zeyu SHEN Qiang WU Shufan Chris J.DAMAREN MU Zhongcheng School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China Institute for Aerospace Studies University of TorontoTorontoOntario M3H 5T6Canada

In this paper,for Multi-Spacecraft System(MSS)with a directed communication topology link and a static virtual leader,a controller is proposed to realize attitude consensus and attitude stabilization with stochastic links failure and actuator ***,an MSS attitude error model suitable for a directed topology link and with a static virtual leader based on SO(3)is derived,which considers that the attitude error on SO(3)cannot be defined based on algebraic ***,we design a controller to realize the MSS on SO(3)with attitude consensus and attitude stabilization under stochastic links failure and actuator ***,the simulation results of a multi-spacecraft system with stochastic links failure and a static virtual leader spacecraft are demonstrated to illustrate the efficiency of the attitude controller.

关键词： Multi-spacecraft systems Attitude consensus Attitude stabilization Stochastic links failure Super-martingale convergence

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Communication Resources Allocation for Time Delay Reduction of Frequency Regulation Service in High Renewable Penetrated Power System

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 468-480页

作者： hongjie He Ning Zhang Chongqing kang Song Ci Fei Teng Goran Strbac State Key Laboratory of Power Systems Department of Electrical EngineeringTsinghua UniversityBeijing 100084China Department of Electrical and Electronic Engineering Imperial College LondonSW72BULondonU.K

The high renewable penetrated power system has severe frequency regulation *** resources can provide frequency regulation services but are limited by com-munication time *** paper proposes a communication resources allocation model to reduce communication time delay in frequency regulation *** device resources and wireless spectrum resources are allocated to distributed resources when they participate in frequency *** reveal impact of communication resources allocation on time delay reduction and frequency regulation ***,we study communication resources allocation solution in high renewable energy penetrated power *** provide a case study based on the HRP-38 *** show communication time delay decreases distributed resources'ability to provide frequency regulation *** the other hand,allocating more communication resources to distributed resources'communica-tion services improves their frequency regulation *** power systems with renewable energy penetration above 70%,required communications resources are about five times as many as 30%renewable energy penetrated power systems to keep frequency performance the *** Terms-Communication resources allocation,commun-ication time delay,distributed resource,frequency regulation,high renewable energy penetrated power system.

关键词： Communication resources allocation communication time delay distributed resource frequency regulation high renewable energy penetrated power system

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Intestinal tuberculosis with small bowel stricture and hemorrhage as the predominant manifestation: Three case reports

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World Journal of Gastrointestinal Surgery 2024年第1期16卷 248-256页

作者： Gang Huang kang-kang Wu Xiao-Na Li Jing-Hua Kuai Ai-Jun Zhang Department of Gastroenterology Qilu Hospital(Qingdao)Cheeloo College of MedicineShandong UniversityQingdao 266000Shandong ProvinceChina

BACKGROUND Intestinal tuberculosis is a chronic disease caused by Mycobacterium tuberculosis that mainly affects the ileum and *** bowel tuberculosis,characterized by predominant involvement of the small intestine,is an extremely rare condition with highly atypical clinical presentations,making diagnosis even more *** SUMMARY We report three cases of small intestinal tuberculosis,two of the patients pre-sented primarily with abdominal pain,and one presented with gastrointestinal *** patients underwent blood tests and imaging *** bowel endoscopy(SBE)revealed that the main lesions in these patients were in-testinal stenosis or gastrointestinal bleeding caused by small intestinal *** patient ultimately underwent surgical *** a complex diagnostic process and comprehensive analysis,all patients were confirmed to have small intestinal tuberculosis and received standard antituberculosis treatment,leading to an improvement in their *** Patients with SBTs present with nonspecific symptoms such as abdominal pain,weight loss,and occasional gastrointestinal *** diagnosis requires a thorough evaluation of clinical symptoms and various tests to avoid misdiagno-sis and complications.

关键词： Intestinal tuberculosis Gastrointestinal hemorrhage Small bowel endoscopy Case report

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