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Mitigating self-excited flame pulsating and thermoacoustic oscillations using perforated liners

Science Bulletin 2019年第13期64卷 941-952页

作者： Dan zhao Ephraim Gutmark Arne Reinecke department of Mechanical Engineering College of EngineeringUniversity of CanterburyChristchurch 8140New Zealand department of Aerospace Engineering and Engineering Mechanics University of CincinnatiCincinnatiOH 45221-0070USA School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore

Open-loop control of self-excited flame pulsating oscillations and thermo-acoustic instability is considered in this *** performance of the control strategy is numerically evaluated in a 2 D Rij ke-type combustor with a perfo rated pipe *** is found that approximately 38 dB sound pressure level(SPL)reduction can be achieved by actively tuning the cooling flow through the perforated ***,the vorticity-induced damping performance is contributing to the breaking up of flame-acoustics ***,the shedding of vortices is not uniformly distributed along the perforated *** apply the control strategy in practice and to validate the findings,experimental studies are performed on a customerdesigned Rij ke-type combustor with a perfo rated liner *** mimic practical engines,a cooling flow generated by a centrifugal pump is provided to pass through the perforated *** tuning the cooling flow rate is found to lead to the unstable combustor being successfully *** is red uced by approximately 35 dB at ω1/2π≈245 Hz,and harmonic thermoacoustic modes are completely *** study is conducted by suddenly re moving the perforated pipe *** combustion system is found to be associated with not only classical thermo-acoustic limit cycle oscillations with a dominant mode at 2.45 × 102 Hz,but also beating oscillations at 1.4 × 1 00 *** is revealed that increasing acoustic losses by implementing the perforated pipe is another critical mechanism contributing to attenuating flame pulsating *** present work opens up an applicable means to attenuate both selfexcited high-frequency thermoacoustic and low-frequency flame pulsating oscillations.

关键词： Flame beating Combustion instability Thermo-acoustic instability Thermal-diffusive instability Perforated pipe Acoustic losses

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催化燃烧对均质压燃发动机排放影响的数值模拟

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燃烧科学与技术 2007年第1期13卷 55-62页

作者：曾文解茂昭贾明大连理工大学动力工程系大连116024

通过耦合deTCHEM软件包及CHEMKIN软件包中的SENKIN模块,对活塞顶涂有催化剂的均质压燃(HCCI)发动机的燃烧过程进行了数值计算,建立了多区模型.利用此模型分析了催化燃烧对HCCI发动机缸内温度、热释放速率以及未燃碳氢化合物(UHC)、氮氧... 详细信息

通过耦合deTCHEM软件包及CHEMKIN软件包中的SENKIN模块,对活塞顶涂有催化剂的均质压燃(HCCI)发动机的燃烧过程进行了数值计算,建立了多区模型.利用此模型分析了催化燃烧对HCCI发动机缸内温度、热释放速率以及未燃碳氢化合物(UHC)、氮氧化合物(NOx)、一氧化碳(CO)排放的影响,结果表明催化燃烧能降低UHC、CO的排放,但NOx的排放会有所升高.对不同催化剂及混合催化剂对HCCI发动机缸内温度、热释放速率以及UHC、NOx、CO排放的影响进行了探索,结果表明,和金属铂相比,以铑作催化剂时UHC的排放降低,但NOx、CO排放会有所升高;采用500/0Pt-500/0Rh的混合催化剂时,UHC、NOx的排放介于1000/0Pt与1000/0Rh之间,但CO的排放却比采用1000/0Pt与1000/0Rh时都要低.

关键词：催化燃烧均质压燃化学动力学模型甲烷排放数值模拟

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Towards the meV limit of the effective neutrino mass in neutrinoless double-beta decays

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Chinese Physics C 2020年第3期44卷 1-11页

作者： Jun Cao Guo-yuan Huang Yu-Feng Li Yifang Wang Liang-Jian wen Zhi-zhong Xing Zhen-hua zhao Shun Zhou Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China department of Physics Liaoning Normal UniversityDalian 116029China

We emphasize that it is extremely important for future neutrinoless double-beta(0νββ)decay experiments to reach the sensitivity to the effective neutrino mass|mββ|≈1 *** such a sensitivity,it is highly possible to discover the signals of 0νββ *** no signal is observed at this sensitivity level,then either neutrinos are Dirac particles or stringent constraints can be placed on their Majorana *** this paper,assuming the sensitivity of|mββ|≈1 meV for future 0νββ decay experiments and the precisions on neutrion oscillation parameters after the JUNO experiment,we fully explore the constrained regions of the lightest neutrino mass m1 and two Majorana-type CP-violating phases{ρ,σ}.Several important conclusions in the case of normal neutrino mass ordering can be ***,the lightest neutrino mass is severely constrained to a narrow range m1∈[0.7,8]meV,which together with the precision measurements of neutrino mass-squared differences from oscillation experiments completely determines the neutrino mass spectrum m2∈[8.6,11.7]meV ing phases is limited to ρ∈[130°,230°],which cannot be obtained from any other realistic ***,the sum of three neutrino masses is found to beΣ≡m1+m2+m3∈[59.2,72.6]meV,while the effective neutrino mass for beta decays turns out to be mβ≡(|Ue1|2m1^2+|Ue2|2m2^2+|Ue3|2m3^2)1/2∈[8.9,12.6]*** observations clearly set up the roadmap for future non-oscillation neutrino experiments aiming to solve the fundamental problems in neutrino physics.

关键词： neutrinoless double-beta decays absolute neutrino masses Majorana CP phases

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Alterations of brain local functional connectivity in amnestic mild cognitive impairment

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Translational Neurodegeneration 2018年第1期7卷 261-274页

作者： Dan Zheng Wei Xia Zhong Quan Yi Pan wen zhao Jian Guo Zhong Hai Cun Shi Hua Liang Li Zhen Yu Dai Ping Lei Pan School of Nursing Jiangsu Vocational College of MedicineYanchengPeople’s Republic of China department of Neurology Affiliated Yancheng HospitalSchool of MedicineSoutheast UniversityWest Xindu Road 2#YanchengJiangsu Province 224001People’s Republic of China department of Central Laboratory Affiliated Yancheng HospitalSchool of MedicineSoutheast UniversityWest Xindu Road 2#YanchengJiangsu Province 224001People’s Republic of China department of Radiology Affiliated Yancheng HospitalSchool of MedicineSoutheast UniversityWest Xindu Road 2#YanchengJiangsu Province 224001People’s Republic of China

Background:Resting-state functional magnetic resonance imaging studies using a regional homogeneity(ReHo)method have reported that amnestic mild cognitive impairment(aMCI)was associated with abnormalities in local functional ***,their results were not ***:Seed-based d Mapping was used to conduct a coordinate-based meta-analysis to identify consistent ReHo alterations in ***:We identified 10 studies with 11 datasets suitable for inclusion,including 378 patients with aMCI and 435 healthy *** meta-analysis identified significant ReHo alterations in patients with aMCI relative to healthy controls,mainly within the default mode network(DMN)(bilateral posterior cingulate cortex[PCC],right angular gyrus,bilateral middle temporal gyri,and left parahippocampal gyrus/hippocampus),executive control network(right superior parietal lobule and dorsolateral prefrontal cortex),visual network(right lingual gyrus and left middle occipital gyrus),and sensorimotor network(right paracentral lobule/supplementary motor area,right postcentral gyrus and left posterior insula).Significant heterogeneity of ReHo alterations in the bilateral PCC,left parahippocampal gyrus/hippocampus,and right superior parietal lobule/angular gyrus was *** meta-regression analyses indicated that general cognitive function,gender distribution,age,and education level partially contributed to this ***:This study provides provisional evidence that aMCI is associated with abnormal ReHo within the DMN,executive control network,visual network,and sensorimotor *** local functional connectivity alterations suggest coexistence of functional deficits and compensation in these *** findings contribute to the modeling of brain functional connectomes and to a better understanding of the neural substrates of *** factors merit much attention and warrant future investigations.

关键词： Amnestic mild cognitive impairment default mode network Meta-analysis Regional homogeneity Resting-state functional magnetic resonance imaging Seed-based d mapping

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Thermoelectric properties of n-type SiGe alloys with Sn incorporation

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Rare Metals 2022年第12期41卷 4156-4163页

作者： Ke Meng La-Mei zhao Ning-Yuan Zhang Zhuang-Fei Zhang Wei-Xia Shen Yue-wen Zhang Biao Wan Chao Fang Liang-Chao Chen Qian-Qian Wang Ju-Long He Xiao-Peng Jia Key Laboratory of Material Physics of Ministry of Education School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao 066004China

In the past several decades,silicon germanium(SiGe)bulk alloys have been a research focus in addressing the current global energy crisis and environmental pollution problems due to their excellent high-temperature thermoelectric *** this study,n-type Si_(80)Ge_(20)P_(2)Sn_(x)bulk alloys were fabricated by spark plasma sintering(SPS)to investigate the effect of Sn *** addition,the optimal sintering conditions and Sn content were *** introduction of Sn improves the electrical conductivity and power factor of the n-type SiGe bulk alloys due to the doping and composite ***,the Si_(80)Ge_(20)P_(2)Sn_(2)bulk alloy could reach a high figure of merit(ZT)value of~1.26 at 800℃.Thus,this work provides a quick preparation method for obtaining n-type SiGe bulk alloys with outstanding thermoelectric properties by incorporating Sn,which is favorable for large-scale production.

关键词： Thermoelectric material Spark plasma sintering(SPS) Silicon germanium alloy Composite

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Strain Rate Effect of AE Characteristics in the Whole Process of Uniaxial Tensile of Mortar

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Journal of Wuhan University of Technology(Materials Science) 2023年第3期38卷 547-556页

作者：王娜王岩 SU Yihui zhao Haitao College of Civil Engineering and Transportation Hohai UniversityNanjing 210024China

We completed the uniaxial tensile test of mortar in the range of strain rate from 10^(-6)to 10^(-4)s^(-1)in the section containing softening,and carried out acoustic emission monitoring(AE)simultaneously.A series of AE parameters and spectrum analysis methods were used to identify the damage evolution process and cracking mechanism of mortar at different strain *** results show that,with the increase of strain rate,the peak stress and tensile elastic modulus of mortar increase obviously,and the stress level corresponding to the starting point of AE activity increases significantly as well,which indicates that the mechanical properties and AE characteristics of mortar have obvious strain rate *** the increase of strain rate,the cumulative AE hit decreases gradually,while the average AE hit rate increases significantly,indicating that the increase of strain rate reduces the damage degree of internal microstructure of the specimen,but the crack propagation speed *** the pre-peak stress stage,the average of AE ringing count and signal energy decreases with the increase of strain rate,while the average of duration increases;in the post-peak stress stage(f_(t)-30%f_(t)),the average of the three AE parameters all increase with the increase of strain rate,indicating that the strain rate effect on the damage process of mortar is different before and after peak stress,and the damage mechanism represented by different parameters is also *** the whole process of uniaxial tensile of mortar,with the increase of strain rate,the scatter distribution of AE frequency-amplitude becomes more discrete,and the b-value shows a decreasing *** addition,the average level of AE peak frequency decreases with the increase of strain rate,while that of ca8 band wavelet energy spectrum coefficient *** is indicated that the increase of strain rate enables the crack propagation state of mortar specimen to become unstable,and the width of macrocrack incre

关键词： mortar acoustic emission uniaxial tension strain rate

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Effects of Rare-earth and Microalloying Elements on the Microstructure Characteristics of Hypereutectoid Rails

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Journal of Wuhan University of Technology(Materials Science) 2023年第3期38卷 682-688页

作者：戴宇恒 zhao wenqian 包喜荣陈林 School of Material and Metallurgy Inner Mongolia University of Science&TechnologyBaotou 014010China Beijing Beiye Functional Materials Corporation Beijing 100000China

We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-earth and microalloying elements on the structure of hypereutectoid rails and optimize the composition design of hypereutectoid *** electron microscopy,transmission electron microscopy,X-ray diffraction,and other characterization techniques were employed to quantitatively analyzed the effects of different microalloying elements,including rare-earth elements,on pearlite lamellar spacing,cementite characteristics,and dislocation *** was found that the lamellar spacing was reduced by adding various microalloying *** lamellar thickness decreased with the refinement of pearlite lamellar spacing while the cementite content per unit volume *** cementite spheroidization,dispersed in the ferrite matrix in granular form and thus playing the role of dispersion strengthening,was observed upon adding cerium(Ce).The contributions of dislocation density to the alloy strength of four steel sheet samples with and without the addition of nickel,Ce,and Ce–copper(Cu)composite were 26,27,32,and 37 MPa,respectively,indicating that the Ce–Cu composite had the highest dislocation strengthening *** Ce–Cu composite has played a meaningful role in the cementite characteristics and dislocation strengthening,which provides a theoretical basis for optimizing the composition design of hypereutectoid rails in actual production conditions.

关键词： microalloying elements rare earth hypereutectoid rail cementite dislocation

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Research of novel complex optical network routing architecture

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The Journal of China Universities of Posts and Telecommunications 2010年第5期17卷 93-99页

作者： HAN Da-hai ZHANG Jie zhao Yong-li zhao Shi-yu Key Laboratory of Information Photonics and Optical Communications Ministry of Education Beijing University of Posts & Telecommtmications Beijing 100876 China

This article puts forward a novel routing architecture for complex optical network,which core component is path calculation element （PCE）.As is well known,the PCE-based distributed path computation structure is making the routing control and computation loosely coupled from traditional control *** the study,the resource allocation and routing algorithm are the critical part of PCE *** compare the performance of new architecture and the traditional one,the user uses the flooding suppression,routing delay,resource utilization and traffic blocking probability as performance simulation parameters and taking the verification simulation on objective modular network testbed （OMNeT） platform against to source-node routing *** numerical analysis,computer simulation and experiment work indicate that the operation of PCE-based routing architecture can reduce the flooding information of path calculation request as well as the routing hops significantly and improve the quality of service （QoS） by decreasing the blocking probability when failure happened.

关键词： complex optical network PCE routing architecture

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Causes and underlying dynamic processes of the mid-winter suppression in the North Pacific storm track

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Science China Earth Sciences 2019年第5期62卷 872-890页

作者： Yuanbing zhao X.San LIANG School of Atmospheric Sciences Nanjing University of Information Science and Technology School of Marine Sciences Nanjing University of Information Science and Technology

Baroclinic wave activity in the North Pacific exhibit peaks in late fall and early spring, and a local minimum in midwinter, when by linear baroclinic instability theory it should attain its maximum. This counterintuitive phenomenon, or"midwinter suppression"(MWM) as called, is investigated with a functional analysis apparatus, multiscale window transform(MWT), and the MWT-based theory of canonical transfer and localized multi-scale energetics analysis, together with a feature tracking technique, using the data from the European Centre for Medium-Range Weather Forecasts ReAnalysis(ERA-40). It is found that the MWM results from a variety of different physical processes, including baroclinic canonical transfer, diabatic effect, energy flux divergence, and frictional dissipation. On one hand, baroclinic canonical transfer and diabatic effect achieve their respective maxima in late fall. More transient available potential energy is produced and then converted to transient kinetic energy, resulting in a stronger storm track in late fall than in midwinter. On the other hand, in early spring, although baroclinic instability and buoyancy conversion are weak, energy flux convergences are substantially strengthened, leading to a net energy inflow into the storm track. Meanwhile, frictional dissipation is greatly reduced in spring; as a result, less transient energy is dissipated in early spring than in midwinter. It is further found that the weakening of baroclinic canonical transfer in midwinter(compared to late fall) is due to the far distance between the storm and the jet stream(located at its southernmost point), which suppresses the interaction between them. Regarding the increase in energy flux convergence in early spring, it appears to originate from the increase(enhancement) in the number(strength) of storms from the upstream into the Pacific.

关键词： Storm track Midwinter suppression Multiscale window transform Multiscale energetics Canonical transfer Energy flux convergence

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A network security entity recognition method based on feature template and CNN-BiLSTM-CRF

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Frontiers of Information Technology & Electronic Engineering 2019年第6期20卷 872-884页

作者： Ya QIN Guo-wei SHEN wen-bo zhao Yan-ping CHEN Miao YU Xin JIN College of Computer Science and Technology Guizhou University Guiyang 550025 China Guizhou Provincial Key Laboratory of Public Big Data Guiyang 550025 China Institute of Information Engineering Chinese Academy of Sciences Beijing 100093 China National Computer Network Emergency Response Technical Team/Coordination Center of China Beijing 100029 China

By network security threat intelligence analysis based on a security knowledge graph(SKG), multi-source threat intelligence data can be analyzed in a fine-grained manner. This has received extensive attention. It is difficult for traditional named entity recognition methods to identify mixed security entities in Chinese and English in the field of network security, and there are difficulties in accurately identifying network security entities because of insufficient features extracted. In this paper, we propose a novel FT-CNN-BiLSTM-CRF security entity recognition method based on a neural network CNN-BiLSTM-CRF model combined with a feature template(FT). The feature template is used to extract local context features, and a neural network model is used to automatically extract character features and text global features. Experimental results showed that our method can achieve an F-score of 86% on a large-scale network security dataset and outperforms other methods.

关键词： Network security entity Security knowledge graph (SKG) Entity recognition Feature template Neural network

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