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Accurate simulations of pure-viscoacoustic wave propagation in tilted transversely isotropic media

Petroleum Science 2024年第2期21卷 866-884页

作者： Qiang Mao jian-Ping Huang Xin-Ru Mu Ji-Dong Yang yu-jian zhang Geosciences Department China University of Petroleum(East China)Qingdao266580ShandongChina Pilot National Laboratory for Marine Science and Technology(Qingdao) Qingdao266207ShandongChina

Forward modeling of seismic wave propagation is crucial for the realization of reverse time migration(RTM) and full waveform inversion(FWI) in attenuating transversely isotropic media. To describe the attenuation and anisotropy properties of subsurface media, the pure-viscoacoustic anisotropic wave equations are established for wavefield simulations, because they can provide clear and stable wavefields. However, due to the use of several approximations in deriving the wave equation and the introduction of a fractional Laplacian approximation in solving the derived equation, the wavefields simulated by the previous pure-viscoacoustic tilted transversely isotropic(TTI) wave equations has low accuracy. To accurately simulate wavefields in media with velocity anisotropy and attenuation anisotropy, we first derive a new pure-viscoacoustic TTI wave equation from the exact complex-valued dispersion formula in viscoelastic vertical transversely isotropic(VTI) media. Then, we present the hybrid finite-difference and low-rank decomposition(HFDLRD) method to accurately solve our proposed pure-viscoacoustic TTI wave equation. Theoretical analysis and numerical examples suggest that our pure-viscoacoustic TTI wave equation has higher accuracy than previous pure-viscoacoustic TTI wave equations in describing q P-wave kinematic and attenuation characteristics. Additionally, the numerical experiment in a simple two-layer model shows that the HFDLRD technique outperforms the hybrid finite-difference and pseudo-spectral(HFDPS) method in terms of accuracy of wavefield modeling.

关键词： Pure-viscoacoustic TTI wave equation Attenuation anisotropy Seismic modeling Low-rank decomposition method

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A Polynomial Prediction Filter Method for Estimating Multisensor Dynamically Varying Biases

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Chinese Journal of Aeronautics 2007年第3期20卷 240-246页

作者： GAO yu zhang jian-qiu HU Bo Department of Electronics Fudan University Shanghai 200433 China

The estimation of the sensor measurement biases in a multisensor system is vital for the sensor data fusion. A solution is provided for the estimation of dynamically varying multiple sensor biases without any knowledge of the dynamic bias model parameters. It is shown that the sensor bias pseudomeasurement can be dynamically obtained via a parity vector. This is accomplished by multiplying the sensor uncalibrated measurement equations by a projection matrix so that the measured variable is eliminated from the equations. Once the state equations of the dynamically varying sensor biases are modeled by a polynomial prediction filter, the dynamically varying multisensor biases can be obtained by Kalman filter. Simulation results validate that the proposed method can estimate the constant biases and dynamic biases of multisensors and outperforms the methods reported in literature.

关键词： signal processing dynamic bias estimation simulation multisensor Kalman filter

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Study on the effect of thermal deformation on the liquid seal of high-temperature molten salt pump in molten salt reactor

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Nuclear Science and Techniques 2023年第2期34卷 128-138页

作者： Xing‑Chao Shen yuan Fu jian‑yu zhang Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The high-temperature molten salt pump is the core equipment in a molten salt reactor that drives the flow of the molten salt *** stability is key to the continuous and reliable operation of the molten salt pump,and the liquid seal at the wear ring can affect the dynamic characteristics of the rotor *** the molten salt pump is operated in the hightemperature molten salt medium,thermal deformation of the submerged parts inevitably occurs,changing clearance between the stator and rotor,affecting the leakage and dynamic characteristics of the *** this study,the seal leakage,seal dynamic characteristics,and rotor system dynamic characteristics are simulated and analyzed using finite element simulation software based on two cases of considering the effect of seal thermal deformation effect or *** results show a significant difference in the leakage characteristics and dynamic characteristics of the seal obtained by considering the effect of seal thermal deformation and neglecting the effect of thermal *** leakage flow rate decreases,and the first-order critical speed of the seal-bearing-rotor system decrease after considering the seal’s thermal deformation.

关键词： High-temperature molten salt pump Seal thermal deformation Leakage characteristics Seal dynamic characteristics Critical speed

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Interactive Web service choice-making based on extended QoS model

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第4期7卷 483-492页

作者： MOU yu-jie CAO jian zhang Shen-sheng zhang jian-hong CIT Lab Department of Computer Science ＆ Technology Shanghai Jiao Tong University Shanghai 200030 China

Quality of Service (QoS) is a key factor in Web service advertising, choosing and runtime monitoring. Web service QoS is multi-faceted, fuzzy and dynamic. Current researches focus on implementation level performance assurance, ignoring domain specific or application level metrics which are also very important to service users. Industry Web service standards lack QoS expression. The support for QoS based service choice-making is very limited. We proposed an extended Web service QoS model based on configurable fuzzy synthetic evaluation system. Web service QoS is evaluated dynamically according to the service context. A QoS requirement description model is also given for service QoS requirement definition. An interactive Web service choice-making process is described, which takes QoS as a key factor when choosing from functionally equivalent services.

关键词： Quality of Service (QoS) Web service Choice-making Fuzzy synthetic evaluation

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Asymptotic energy efficiency analysis for the state-of-the-art relaying protocols

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The Journal of China Universities of Posts and Telecommunications 2011年第6期18卷 8-13页

作者： WANG yu-ning zhang jian-hua XU Wei Key Lab of Universal Wireless Communications Ministry of Education Wireless Technology Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China

This article analyzes the energy-efficiency performances of fixed relaying schemes, selection relaying schemes and incremental relaying schemes in the three-node relay network. The closed-form asymptotic energy per good-bit （EPG） expressions for the state-of-the-art relaying protocols at high signal-to-noise ratio （SNR） regime are derived. In the formulation of the energy consumption model, the transmission, circuit and retransmission energies are all taken into account. To facilitate the comparison of energy-efficiency performances between different relaying protocols, the link reliabilities and retransmission probabilities are determined by the asymptotic outage probabilities at high SNR regime under the Rayleigh fading assumption. Computer simulations are carried out in both symmetric and asymmetric relay networks. The simulation results show the differences of system energy expenditure between these state-of-the-art relaying protocols. Finally some practical implications can be made from the observation.

关键词： green communication EPG relay energy-efficiency outage probability

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Effects of UV-A exposures on longevity and reproduction in Helicoverpa armigera, and on the development of its F1 generation

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Insect Science 2011年第6期18卷 697-702页

作者： Chang-yu zhang jian-yu Meng Xiao-Ping Wang Fen Zhu Chao-Liang Lei Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory College of Plant Science and TechnologyHuazhong Agricultural University Wuhan China

Helicoverpa armigera adults display a conspicuous positive phototactic behavior to light stimuli, and are especially sensitive to ultraviolet （UV） light. The effects of UV-A （longwave） exposures on adult longevity and reproduction in H. armigera were investigated, as well as the development of the Ft generation. Paired adults were exposed to UV-A for various time periods （0, 1, 5 and 9 h/day）, until the end of adult life. The results showed that adult longevity decreased with increasing exposure time for both sexes, and a significant decrease was observed after exposure for 5 and 9 h/day. Fecundity increased when adults were exposed for 1 and 5 h/day, and a significant difference was observed in the 5 h/day group. Oviposition rates of females in all treatments were significantly higher than in the control. Exposure to UV-A for longer periods （5 and 9 h/day） caused a decline in cumulative survival of F1 immature stages, but no significant differences were found in egg hatch, pupation and eclosion. The developmental periods of F1 larvae were significantly prolonged after exposure to UV-A for 5 and 9 h/day. UV-A radiation had no significant effects on F1 pupal period.

关键词： development Helicoverpa armigera longevity oxidative stress,reproduction UV-A

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Posterior Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis Patients:a Comparison of All Pedicle Screws versus Hybrid Instrumentation

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Chinese Medical Sciences Journal 2009年第1期24卷 30-35页

作者： Bin yu jian-guo zhang Gui-xing Qiu Yi-peng Wang yu Zhao jian-xiong Shen Hong Zhao Xin-yu Yang Department of Orthopedic Surgery Peking Union Medical College HospitalChinese Academy of Medical Sciences ＆ Peking Union Medical CollegeBeijing 100730 China

Objective To analyze the influence of segmental pedicle screws versus hybrid instrumentation on the correction results in adolescent idiopathic scoliosis patients undergoing posterior selective thoracic fusion. Methods By reviewing the medical records and roentgenograms of adolescent idiopathic scoliosis patients who underwent selective thoracic fusion from February 2000 to January 2007 in our hospital, the patients were divided into 2 groups according to different instrumentation fashions： Group A was hook-screw-rod （hybrid） internal fixation type, Group B was screw-rod （all pedicle screws） internal fixation type, and the screws were used in every segment on the concave side of the thoracic curve. The parameters of the scoliosis were measured and the correction results were analyzed. Results Totally, 48 patients （7 males, 41 females） were included, with an average age of 14.4 years old and a mean follow-up time of 12.3 months. Thirty and 18 patients were assigned to group A and group B, respectively. The mean preoperative coronal Cobb angles of the thoracic curve were 48.8° and 47.4°, respectively. After surgery, they were corrected to 13.7° and 6.8°, respectively. At final follow-up, they were 17.0° and 9.5°, with an average correction rate of 64.6% and 79.0%, respectively, and the correction rate of group B was significantly higher than that of group A （P=0.003）. The mean preoperative coronal Cobb angles of the lumbar curve were 32.6° and 35.2°, respectively. After surgery, they were corrected to 8.6° and 8.3°, respectively. At final follow-up, they were 10.3° and 11.1°, with an average correction rate of 66.8% and 69.9%, respectively, and the correction rate of group B was significantly higher than that of group A （P=0.003）. The correction loss of the thoracic curve and lumbar curve in the 2 groups were 3.1° and 1.8°, 2.4° and 2.4°, respectively. No significant difference was noted （both P〉0.05）. The decompensation rate at final follow-up in these 2 groups wer

关键词： adolescent idiopathic scoliosis selective thoracic fusion internal fixator pedicle screw decompensation

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Facile synthesis of high-brightness green-emitting carbon dots with narrow bandwidth towards backlight display

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Chinese Chemical Letters 2024年第5期35卷 277-282页

作者： Rui Cheng Tingting zhang Xin Huang jian yu State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 210009China

High-performance carbon dots(CDs)allowing the application in high-end display devices are highly desirable and usually limited by the absence of simple and easy synthesis *** this work,we exploited an easy-to-implement strategy for the one-step synthesis of green-emitting CDs(G-CDs)with superb optical *** G-CDs were synthesized using m-phenylenediamine(m-PD)as a single precursor,and the reaction reacted at 180℃for 12 h The resultant G-CDs exhibit high-purity and excitationindependent green fluorescence with the photoluminescence(PL)peak located at 516 nm,full width at half maximum(FWHM)of 46 nm,and PL quantum yield(QY)of∼80%under the 470nm excitation *** G-CDs and corresponding composite film prepared with polyvinyl butyral(G-CDs@PVB)exhibit good PL stability after undergoing long-time storage for one year and 360 h exposure under 460nm blue *** G-CDs@PVB film was used as color-conversion materials in green-emitting light-emitting diode(LED)application,exhibiting a Commission internationale de l’Eclairage(CIE)chromaticity coordinate of(0.21,0.44).The film was also used in CD-based liquid crystal display(CD-LCD)application,achieving a color gamut value of 85%.This work will offer a working basis for the synthesis of high-performance CDs as well as their application in displays.

关键词： Carbon dots One-step synthesis Narrow bandwidth High quantum yield Display

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Exploring changes of precipitation extremes under climate change through global variable-resolution modeling

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Science Bulletin 2024年第2期69卷 237-247页

作者： Wei Sun jian Li Rucong yu Nina Li Yi zhang State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China Institute of Tibetan Plateau Meteorology China Meteorological AdministrationChengdu 610072China Department of Atmospheric Science Yunnan UniversityKunming 650091China National Meteorological Center China Meteorological AdministrationBeijing 100081China 2035 Future Laboratory PIESAT Information Technology Co.Ltd.Beijing 100105China

Understanding the responses of precipitation extremes to global climate change remains limited owing to their poor representations in models and complicated interactions with multi-scale *** we take the record-breaking precipitation over China in 2021 as an example,and study its changes under three different climate scenarios through a developed pseudo-global-warming(PGW)experimental framework with 60-3 km variable-resolution global ensemble *** to the present climate,the precipitation extreme under a warmer(cooler)climate increased(decreased)in intensity,coverage,and total amount at a range of 24.3%-37.8%(18.7%-56.1%).With the help of the proposed PGW experimental framework,we further reveal the impacts of the multi-scale system interactions in climate change on the precipitation *** the warmer climate,large-scale water vapor transport converged from double typhoons and the subtropical high marched into central China,enhancing the convective energy and instability on the leading edge of the transport *** a result,the mesoscale convective system(Mcs)that directly contributed to the precipitation extreme became stronger than that in the present *** the contrary,the cooler climate displayed opposite changing characteristics relative to the warmer climate,ranging from the large-scale systems to local environments and to the *** summary,our study provides a promising approach to scientifically assess the response of precipitation extremes to climate change,making it feasible to perform ensemble simulations while investigating the multi-scale system interactions over the globe.

关键词： Precipitation extreme Climate change Pseudo-global-warming experiment Variable-resolution modeling Multi-scale system interaction

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VIDEO-ASSISTED THORACOSCOPIC CORRECTION AND FUSION OF SCOLIOSIS

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Chinese Medical Sciences Journal 2007年第3期22卷 144-151页

作者： Bin yu jian-guo zhang Gui-xing Qiu Yi-peng Wang Xin-yu Yang Department of Orthopedics Peking Union Medical College Hospital Chinese Academy of Medical Sciences ＆ Peking Union Medical College Beijing 100730

Objective To evaluate the operative technique and preliminary results of video-assisted thoracoscopic anterior correction and fusion of scoliosis. Methods Eleven cases underwent thoracoscopic anterior correction and fusion of scoliosis from March 2003 to April 2005 in our hospital were reviewed. They were all females with an average age of 13.1 years old. Of which, 9 cases were idiopathic scoliosis, 1 case was congenital scoliosis, and 1 case was Marian syndrome scoliosis. The coronal Cobb angle and apical vertebral translation before and after surgery as well as at final follow-up were measured. The operation time, blood loss during operation, and peri-operative complications were recorded. The mean operation time was 6. 4 hours, mean instrumented vertebrae were 6.4 segments, and mean blood loss during operation was 364 mU The coronal Cobb angles of the thoracic curve before and after surgery were 45.5° and 15.4° respectively, with an average correction rate of 65.4%. The lumbar curve was corrected from 28.4° to 11.8° , with an average simultaneous correction rate of 57.2%. All of the patients were followed up regularly with an average time of 21.4 months. At the final foUow-up, the coronal Cobb angles of the thoracic and lumbar curves were 19.0° and 20. 1° , with a 3.6° and 8. 3° loss of correction, respectively. The apical vertebral translation was improved from 32. 3 mm to 10.5 mm for the thoracic curve, and from 13.1 mm to 8.2 mm for the lumbar curve. There were 6 cases with peri-opemtive complications, including 1 case of thoracic effusion, 1 case of chylothomx, 1 case of locking plug loosing, 2 cases of aggravation of the unfused lumbar curve （ 1 case also with thoracolumbar kyphosis）, and 1 case with a screw tip causing a contour deformity of the aorta. And 4 of them underwent revision surgery.Conclusions Video-assisted thoracoscopic anterior correction and fusion of scoliosis has good correction capability, less intraoperative bleeding, and favorable

关键词： scoliosis anterior fusion thoracoscopy intemal fixation

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