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Relative carrier-envelope phase dependence of resonant propagation of two-colour femtosecond pulses in V-type atomic medium 被引量:1
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作者 谭霞 王振东 +1 位作者 王蕾 樊锡君 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第6期349-355,共7页
Using numerical solution of the full Maxwell-Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor-orrector method, we investigate the modulation effect of relative... Using numerical solution of the full Maxwell-Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor-orrector method, we investigate the modulation effect of relative carrierenvelope phase (hereinafter referred to as the relative phase) on resonant propagation of two-colour femtosecond ultrashort laser pulses in a V-type three-level atomic medium. It is found that the pulse splitting occurs for a smaller value of relative phase; when the value of relative phase increases to a certain value, only the variation of pulse shape is present and the pulse splitting does not occur any more; moreover, when the value of relative phase is smaller, the pulse group velocity is larger. The relative phase also has an obvious effect on population and spectral property. Different population transfers can be realized by adjusting the value of relative phase. Generally speaking, for the pulses with smaller areas their spectral strengths and frequency ranges decrease obviously with the value of relative phase increasing; for the pulses with larger areas, with value of the relative phase increasing, their spectral strengths decrease remarkably but the relative strengths of the higher frequency components increase significantly, while the spectral frequency range is not varied evidently. 展开更多
关键词 two-colour ultrashort pulses relative carrier envelope phase resonant propagation V- type three-level atomic medium
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Carrier Envelope Phase Description for an Isolated Attosecond Pulse by Momentum Vortices 被引量:1
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作者 Meng Li Gui-zhong Zhang +1 位作者 Xin Ding Jian-quan Yao 《Chinese Physics Letters》 SCIE CAS CSCD 2019年第6期24-28,共5页
As a crucial parameter for a few-cycle laser pulse, the carrier envelope phase(CEP) substantially determines the laser waveform. We propose a method to directly describe the CEP of an isolated attosecond pulse(IAP) by... As a crucial parameter for a few-cycle laser pulse, the carrier envelope phase(CEP) substantially determines the laser waveform. We propose a method to directly describe the CEP of an isolated attosecond pulse(IAP) by the vortex-shaped momentum pattern, which is generated from the tunneling ionization of a hydrogen atom by a pair of time-delayed, oppositely and circularly polarized IAP-IR pulses. Superior to the angular streaking method that characterizes the CEP in terms of only one streak, our method describes the CEP of an IAP by the features of multiple streaks in the vortex pattern. The proposed method may open the possibility of capturing sub-cycle extreme ultraviolet dynamics. 展开更多
关键词 ISOLATED ATTOsecond Pulse MOMENTUM VORTICES carrier ENVELOPE phase(CEP)
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Femtosecond Time-Resolved Spectroscopic Photoemission Electron Microscopy for Probing Ultrafast Carrier Dynamics in Heterojunctions 被引量:1
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作者 Bo-han Li Guan-hua Zhang +6 位作者 Yu Liang Qun-qing Hao Ju-long Sun Chuan-yao Zhou You-tian Tao Xue-ming Yang Ze-feng Ren 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2019年第4期399-405,I0002,共8页
The fast developing semiconductor industry is pushing to shrink and speed up transistors. This trend requires us to understand carrier dynamics in semiconductor heterojunctions with both high spatial and temporal reso... The fast developing semiconductor industry is pushing to shrink and speed up transistors. This trend requires us to understand carrier dynamics in semiconductor heterojunctions with both high spatial and temporal resolutions. Recently, we have successfully set up a timeresolved photoemission electron microscopy (TR-PEEM), which integrates the spectroscopic technique to measure electron densities at specific energy levels in space. This instrument provides us an unprecedented access to the evolution of electrons in terms of spatial location, time resolution, and energy, representing a new type of 4D spectro-microscopy. Here in this work, we present measurements of semiconductor performance with a time resolution of 184 fs, electron kinetic energy resolution of 150 meV, and spatial resolution of about 150 nm or better. We obtained time-resolved micro-area photoelectron spectra and energy-resolved TR-PEEM images on the Pb island on Si(111). These experimental results suggest that this instrument has the potential to be a powerful tool for investigating the carrier dynamics in various heterojunctions, which will deepen our understanding of semiconductor properties in the submicron/nanometer spatial scales and ultrafast time scales. 展开更多
关键词 Time resolution Photoemission electron microscopy Ultrafast carrier dynamics Photoelectron spectroscopy
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Studying the charge carrier properties in CuInS_2 films via femtosecond transient absorption and nanosecond transient photocurrents
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作者 Mingrui Tan Qinghui Liu +6 位作者 Ning Sui Zhihui Kang Liquan Zhang Hanzhuang Zhang Wenquan Wang Qiang Zhou Yinghui Wang 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第5期222-225,共4页
The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change ... The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photogenerated charge carriers are extracted by a bias electric field E in the nanosecond transient photocurrent system. An applied E improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS_2 thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of E. Our results provide useful insights into the characteristics of carriers in the CuInS_2 thin film and are important for the operation of optoelectronic devices realized with these films. 展开更多
关键词 SEMICONDUCTOR film carrier dynamics TRANSIENT ABSORPTION TRANSIENT PHOTOCURRENT
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基于Tv-SECOND的自动驾驶场景下的3D目标检测
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作者 魏海跃 杨奎河 毕江峰 《无线电通信技术》 北大核心 2024年第4期823-830,共8页
针对自动驾驶场景中复杂环境下的3D目标检测任务,特别是远距离和遮挡条件下,为提高模型的检测准确率,在SECOND的基础上提出了Tv-SECOND两阶段算法。该算法提出一种基于Transformer架构的提案框特征提取模块,并在传统体素特征编码基础上... 针对自动驾驶场景中复杂环境下的3D目标检测任务,特别是远距离和遮挡条件下,为提高模型的检测准确率,在SECOND的基础上提出了Tv-SECOND两阶段算法。该算法提出一种基于Transformer架构的提案框特征提取模块,并在传统体素特征编码基础上提出可变形的体素特征编码模块。在KITTI数据集上进行测试,结果显示,所提出的算法相比SECOND在远距离和遮挡严重的情况下分别提高了7.49%、9.72%。同时与其他先进的两阶段方法相比,检测精度有不同程度的提升,证明了Tv-SECOND算法的有效性。新算法能够建立特征之间的依赖关系,聚合周边广域的上下文信息,增强模型的学习推理能力,有效提升了模型在远距离和遮挡的情况下的检测性能。 展开更多
关键词 自动驾驶 3D目标检测 TRANSFORMER second
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Carrier rate of hepatitis B surface antigen (HBsAg) among urban pregnant women in a secondary health facility in Maiduguri, Northeastern Nigeria
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作者 David Nadeba Bukbuk Maxwell Bayo Samaila +2 位作者 Akawu Denue Ballah Ibrahim Musa Kida Chima Iwuoha 《World Journal of Cardiovascular Diseases》 2013年第8期512-518,共7页
A serological survey conducted among 196 pregnant women resident in and around Maiduguri, an urban town in north eastern Nigeria showed that 33 (16.8%) were asymptomatic carriers of hepatitis B virus surface antigen (... A serological survey conducted among 196 pregnant women resident in and around Maiduguri, an urban town in north eastern Nigeria showed that 33 (16.8%) were asymptomatic carriers of hepatitis B virus surface antigen (HBsAg). They are within the age range of 14-40 years with mean (± SD) age of 24.7 (± 6.3). The women attend antenatal clinic at the State Specialist Hospital, a secondary health facility in Maiduguri, Borno state. The women are all heterosexuals. The distribution of HBsAg carrier rate according to age of women studied showed a significant (p = 0.0061) increase of the prevalence of HBsAg from 4 (8.7%) in the lower age group (39 years). According to the number of pregnancies, the prevalence of HBsAg infection increased significantly from 6 (9.2%) among primiparous to 13 (13.7%) and 14 (38.9%) among multiparous and grand multiparous respectively. The carrier rate of HBsAg infection among the pregnant women studied based on their duration of pregnancies and their social class showed no significant differences. However, according to the factors known to be commonly associated with the highest risk of transmission of HBV such as history of blood transfusion, Tribal marks/tattooing, use of sharps, sharing of articles, history of jaundice in the women and husbands, history of sexually transmitted infections (STIs) of the women and husbands and the type of marriage (monogamous or polygamous), number of sexual relationships per week, only the history of blood transfusion was significantly associated with HBsAg carrier rate (RR = 3.71., 95% Confidence Interval (C.I.), 1.89-7.30, p = 0.0078). The study confirms that pregnant women who attend antenatal clinic in this secondary health facility are at higher risk of being infected with the HBV, which could lead to both prenatal and post natal transmission to their newborns. 展开更多
关键词 carrier Rate HBSAG URBAN PREGNANT Women SSH Borno State NIGERIA
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The Extended Hybrid Carrier-Based Multiple Access Technology for High Mobility Scenarios 被引量:1
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作者 Ge Song Xiaojie Fang Xuejun Sha 《China Communications》 SCIE CSCD 2024年第1期53-68,共16页
The hybrid carrier(HC)system rooted in the carrier fusion concept is gradually garnering attention.In this paper,we study the extended hybrid carrier(EHC)multiple access scheme to ensure reliable wireless communicatio... The hybrid carrier(HC)system rooted in the carrier fusion concept is gradually garnering attention.In this paper,we study the extended hybrid carrier(EHC)multiple access scheme to ensure reliable wireless communication.By employing the EHC modulation,a power layered multiplexing framework is realized,which exhibits enhanced interference suppression capability owing to the more uniform energy distribution design.The implementation method and advantage mechanism are explicated respectively for the uplink and downlink,and the performance analysis under varying channel conditions is provided.In addition,considering the connectivity demand,we explore the non-orthogonal multiple access(NOMA)method of the EHC system and develop the EHC sparse code multiple access scheme.The proposed scheme melds the energy spread superiority of EHC with the access capacity of NOMA,facilitating superior support for massive connectivity in high mobility environments.Simulation results have verified the feasibility and advantages of the proposed scheme.Compared with existing HC multiple access schemes,the proposed scheme exhibits robust bit error rate performance and can better guarantee multiple access performance in complex scenarios of nextgeneration communications. 展开更多
关键词 extended hybrid carrier system high mo-Received:Jun.09 2023 Revised:Nov.20 2023 Editor:Yuanwei Liu bility communications multiple access
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Thermogravimetric characteristics of corn straw and bituminous coal copyrolysis based the ilmenite oxygen carriers
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作者 Pengxing Yuan Xiude Hu +2 位作者 Jingjing Ma Tuo Guo Qingjie Guo 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第4期8-15,共8页
Herein,the co-pyrolysis reaction characteristics of corn straw(CS)and bituminous coal in the presence of ilmenite oxygen carriers(OCs)are investigated via thermogravimetry coupled with mass spectrometry.The results re... Herein,the co-pyrolysis reaction characteristics of corn straw(CS)and bituminous coal in the presence of ilmenite oxygen carriers(OCs)are investigated via thermogravimetry coupled with mass spectrometry.The results reveal that the participation of OCs weakens the devolatilization intensity of co-pyrolysis.When the CS blending ratio is<50%,the mixed fuel exhibits positive synergistic effects.The fitting results according to the Coats-Redfern integral method show that the solid-solid interaction between OCs and coke changes the reaction kinetics,enhancing the co-pyrolysis reactivity at the high-temperature zone(750-950C).The synergistic effect is most prominent at a 30%CS blending ratio,with copyrolysis activation energy in the range of 26.35-40.57 kJ·mol^(-1). 展开更多
关键词 Oxygen carrier CO-PYROLYSIS BIOMASS COAL
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Regulation of the quantum barrier and carrier transport toward high-efficiency quasi-2D Dion-Jacobson tin perovskite solar cells
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作者 Huanhuan Yao Chang Shi +5 位作者 Tai Wu Shurong Wang Mingyu Yin Liming Ding Yong Hua Feng Hao 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第8期200-207,I0005,共9页
Quasi-2D Dion-Jacobson(DJ)tin halide perovskite has attracted much attention due to its elimination of Van der Waals gap and enhanced environmental stability.However,the bulky organic spacers usually form a natural qu... Quasi-2D Dion-Jacobson(DJ)tin halide perovskite has attracted much attention due to its elimination of Van der Waals gap and enhanced environmental stability.However,the bulky organic spacers usually form a natural quantum well structure,which brings a large quantum barrier and poor film quality,further limiting the carrier transport and device performance.Here,we designed three organic spacers with different chain lengths(ethylenediamine(EDA),1,3-propanediamine(PDA),and 1,4-butanediamine(BDA))to investigate the quantum barrier dependence.Theoretical and experimental characterizations indicate that EDA with short chain can reduce the lattice distortion and dielectric confinement effect,which is beneficial to the effective dissociation of excitons and the inhibition of trap-free non-radiative relaxation.In addition,EDA cation shows strong interaction with the inorganic octahedron,realizing large aggregates in precursor solution and high-quality films with improved structural stability.Furthermore,femtosecond transient absorption proves that EDA cations can also weaken the formation of small n-phases with large quantum barrier to achieve effective carrier transport between different nphases.Finally,the quasi-2D DJ(EDA)FA_(9)Sn_(10)I_(31)solar cells achieves a 7.07%power conversion efficiency with good environment stability.Therefore,this work sheds light on the regulation of the quantum barrier and carrier transport through the chain length of organic spacer for qua si-2D DJ lead-free perovskites. 展开更多
关键词 Chain lengths Organic spacers Quantum well carrier transport Lattice distortion
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Clinical Analysis and Mental Health Survey of Hemophilia Carriers:a Cross-sectional Study
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作者 Wen WANG Li-juan JIANG +4 位作者 Dong-yan CUI Ai ZHANG Xiong WANG Ai-guo LIU Qun HU 《Current Medical Science》 SCIE CAS 2024年第2期435-440,共6页
Objective:Hemophilia carriers(HCs),who are heterozygous for mutations in the clotting factor VIII/clotting factor IX gene(F8 or F9),may have a wide range of clotting factor levels,from very low,similar to afflicted ma... Objective:Hemophilia carriers(HCs),who are heterozygous for mutations in the clotting factor VIII/clotting factor IX gene(F8 or F9),may have a wide range of clotting factor levels,from very low,similar to afflicted males,to the upper limit of normal,and may experience mental health issues.The purpose of this study was to provide genetic information on mothers of hemophilia patients and to understand the clotting factor activity and phenotype of HCs.Additionally,we aimed to investigate the mental health status of HCs in China.Methods:A total of 127 hemophilia mothers,including 93 hemophilia A(HA)mothers and 34 hemophilia B(HB)mothers,were enrolled in this study.Long distance PCR,multiplex PCR,and Sanger sequencing were used to analyze mutations in F8 or F9.Coagulation factor activity was detected by a one-stage clotting assay.The Symptom Checklist 90(SCL-90,China/Mandarin version)was given to HCs at the same time to assess their mental health.Results:A total of 90.6%of hemophilia mothers were diagnosed genetically as carriers,with inversion in intron 22 and missense mutations being the most common mutation types in HA and HB carriers,respectively.The median clotting factor level in carriers was 0.74 IU/mL(ranging from 0.09 to 1.74 IU/mL)compared with 1.49 IU/mL(ranging from 0.93 to 1.89 IU/mL)in noncarriers,of which 14.3%of HCs had clotting factor levels of 0.40 IU/mL or below.A total of 53.8%(7/13)of HA carriers with low clotting factor levels(less than 0.50 IU/mL)had a history of bleeding,while none of the HB carriers displayed a bleeding phenotype.The total mean score and the global severity index of the SCL-90 for surveyed HCs were 171.00(±60.37)and 1.78(±0.59),respectively.A total of 67.7%of the respondents had psychological symptoms,with obsessive-compulsive disorder being the most prevalent and severe.The pooled estimates of all nine factors were significantly higher than those in the general population(P<0.05).Conclusions:The detection rate of gene mutations in hemophilia mothers was 90.6%,with a median clotting factor level of 0.74 IU/mL,and 14.3%of HCs had a clotting factor level of 0.40 IU/mL or below.A history of bleeding was present in 41.2%of HCs with low clotting factor levels(less than 0.50 IU/mL).Additionally,given the fragile mental health status of HCs in China,it is critical to develop efficient strategies to improve psychological well-being. 展开更多
关键词 hemophilia A hemophilia B MUTATION carrier mental health
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Vertical plane depth-resolved surface potential and carrier separation characteristics in flexible CZTSSe solar cells with over 12% efficiency
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作者 Dae-Ho Son Ha Kyung Park +11 位作者 Dae-Hwan Kim Jin-Kyu Kang Shi-Joon Sung Dae-Kue Hwang Jaebaek Lee Dong-Hwan Jeon Yunae Cho William Jo Taeseon Lee JunHo Kim Sang-Hoon Nam Kee-Jeong Yang 《Carbon Energy》 SCIE EI CAS CSCD 2024年第3期36-52,共17页
Cu2ZnSn(S,Se)4(CZTSSe)solar cells have resource distribution and economic advantages.The main cause of their low efficiency is carrier loss resulting from recombination of photo-generated electron and hole.To overcome... Cu2ZnSn(S,Se)4(CZTSSe)solar cells have resource distribution and economic advantages.The main cause of their low efficiency is carrier loss resulting from recombination of photo-generated electron and hole.To overcome this,it is important to understand their electron-hole behavior characteristics.To determine the carrier separation characteristics,we measured the surface potential and the local current in terms of the absorber depth.The elemental variation in the intragrains(IGs)and at the grain boundaries(GBs)caused a band edge shift and bandgap(Eg)change.At the absorber surface and subsurface,an upward Ec and Ev band bending structure was observed at the GBs,and the carrier separation was improved.At the absorber center,both upward Ec and Ev and downward Ec-upward Ev band bending structures were observed at the GBs,and the carrier separation was degraded.To improve the carrier separation and suppress carrier recombination,an upward Ec and Ev band bending structure at the GBs is desirable. 展开更多
关键词 carrier separation CZTSSe flexible solar cell local current surface potential
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Advancements in biomass gasification research utilizing iron-based oxygen carriers in chemical looping:A review
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作者 Yonghong Niu Zhengyang Chi Ming Li 《Materials Reports(Energy)》 EI 2024年第3期35-48,共14页
Biomass,recognized as renewable green coal,is pivotal for energy conservation,emission reduction,and dualcarbon objectives.Chemical looping gasification,an innovative technology,aims to enhance biomass utilization eff... Biomass,recognized as renewable green coal,is pivotal for energy conservation,emission reduction,and dualcarbon objectives.Chemical looping gasification,an innovative technology,aims to enhance biomass utilization efficiency.Using metal oxides as oxygen carriers regulates the oxygen-to-fuel ratio to optimize synthesis product yields.This review examines various oxygen carriers and their roles in chemical looping biomass gasification,including natural iron ore types,industrial by-products,cerium oxide-based carriers,and core-shell structures.The catalytic,kinetic,and phase transfer properties of iron-based oxygen carriers are analyzed,and their catalytic cracking capabilities are explored.Molecular interactions are elucidated and system performance is optimized by providing insights into chemical looping reaction mechanisms and strategies to improve carrier efficiency,along with discussing advanced techniques such as density functional theory(DFT)and reactive force field(ReaxFF)molecular dynamics(MD).This paper serves as a roadmap for advancing chemical looping gasification towards sustainable energy goals. 展开更多
关键词 Chemical looping gasification Iron based oxygen carrier Preparation of oxygen carrier system
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Optimizing the sulfur-resistance and activity of perovskite oxygen carrier for chemical looping dry reforming of methane
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作者 Yuelun Li Dong Tian +6 位作者 Lei jiang Huicong Zuo LiNan Huang Mingyi Chen Jianchun Zuo Hua Wang Kongzhai Li 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第9期259-271,共13页
Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane,but they are easily inactivated by the presence of trace H_(2)S.Here,we propose to modu... Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane,but they are easily inactivated by the presence of trace H_(2)S.Here,we propose to modulate both the activity and resistance to sulfur poisoning by dual substitution of Mo and Ni ions with the Fe-sites of LaFeO_(3)perovskite.It is found that partial substitution of Ni for Fe substantially improves the activity of LaFeO_(3)perovskite,while Ni particles prefer to grow and react with H_(2)S during the long-term successive redox process,resulting in the deactivation of oxygen carriers.With the presence of Mo in LaNi_(0.05)Fe_(0.95)O_(3−σ)perovskite,H_(2)S preferentially reacts with Mo to generate MoS_(2),and then the CO_(2)oxidation can regenerate Mo via removing sulfur.In addition,Mo can inhibit the accumulation and growth of Ni,which helps to improve the redox stability of oxygen carriers.The LaNi_(0.05)Mo_(0.07)Fe_(0.88)O_(3−σ)oxygen carrier exhibits stable and excellent performance,with the CH_(4)conversion higher than 90%during the 50 redox cycles in the presence of 50 ppm H_(2)S at 800℃.This work highlights a synergistic effect in the perovskite oxides induced by dual substitution of different cations for the development of high-performance oxygen carriers with excellent sulfur tolerance. 展开更多
关键词 Perovskite oxygen carriers Chemical looping reforming Sulfur-resistance Dual substitution SYNGAS
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Identifying the effect of photo-generated carriers on the phonons in rutile TiO_(2) through Raman spectroscopy
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作者 Zheng Wang Min Liao +1 位作者 Guihua Wang Meng Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第11期422-428,共7页
Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials.Carriers can interact with lattices and influence lattice vibrations;thus,it is feasible to study the ... Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials.Carriers can interact with lattices and influence lattice vibrations;thus,it is feasible to study the effect of photo-generated carriers on phonons by analyzing changes in the Raman spectra of semiconductors.Rutile is one of the predominant crystalline phases of TiO_(2),which is a widely utilized metal oxide semiconductor.In this work,rutile TiO_(2) is coated on a thinned optical fiber to concentrate ultraviolet light energy within the material,thereby enhancing the generation of carriers and amplifying the changes in the Raman spectra.A Raman detection laser with a wavelength of 532 nm is utilized to collect the Raman spectra of rutile TiO_(2) during irradiation.Using this setup,the impact of photo-generated carriers on the phonons corresponding to Raman vibrational modes is researched.The localization and non-radiative recombination of photo-generated carriers contribute to a reduction in both the frequencies and lifetimes of phonons.This work provides a novel approach to researching the effect of carriers on phonons. 展开更多
关键词 Raman spectroscopy photo-generated carriers rutile TiO_(2) PHONONS
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Ultrafast carrier dynamics in GeSn thin film based on time-resolved terahertz spectroscopy
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作者 黄盼盼 张有禄 +3 位作者 胡凯 齐静波 张岱南 程亮 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期164-169,共6页
We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn un... We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications. 展开更多
关键词 GeSn thin film time-resolved THz spectroscopy ultrafast dynamics carrier recombination
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Ethane Chemical Looping Oxidative Dehydrogenation to Ethylene over Co_(2)O_(3)(Fe_(2)O_(3),NiO)/LaCoO_(3) Oxygen Carriers
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作者 Liang Hao Meng Jinhong +1 位作者 Sun Jie Wei Dongkai 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS CSCD 2024年第3期33-41,共9页
Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for converting ethane to ethylene.In the current study MeO/LaCoO_(3)(MeO=Fe_(2)O_(3),NiO or Co_(2)O_(3))composite metal oxides w... Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for converting ethane to ethylene.In the current study MeO/LaCoO_(3)(MeO=Fe_(2)O_(3),NiO or Co_(2)O_(3))composite metal oxides were prepared via citrate gel and impregnation methods,and used as oxygen carriers for CL-ODH.X-ray diffraction results indicated that all oxygen carriers had a perovskite structure even after eight redox cycles.Under a reaction temperature of 650°C,a reaction pressure of 0.1 MPa,and a weight hourly space velocity(WHSV)of 7500 mL/(g·h),ethane conversion over Co_(2)O_(3)/LaCoO_(3) reached 100%and ethylene selectivity reached 60%,both of which were better than corresponding values attained over Fe_(2)O_(3)/LaCoO_(3) and NiO/LaCoO_(3).Ethylene selectivity remained stable for 80 cycles over Co_(2)O_(3)/LaCoO_(3),then decreased gradually after 80 cycles.X-ray photoelectron spectroscopy results and evaluation results indicated that lattice oxygen and O_(2)2-had a direct relationship with ethane conversion and ethylene selectivity.Co_(2)O_(3)/LaCoO_(3) exhibited a strong capacity to release and absorb oxygen,mainly due to interaction between Co_(2)O_(3) and LaCoO_(3). 展开更多
关键词 chemical looping oxidative dehydrogenation ETHANE ETHYLENE oxygen carrier PEROVSKITE
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Experimental Study on Gas Flow Uniformity in a Diesel Particulate Filter Carrier
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作者 Zhengyong Wang Jianhua Zhang +5 位作者 Guoliang Su Peixing Yang Xiantao Fan Shuzhan Bai Ke Sun Guihua Wang 《Fluid Dynamics & Materials Processing》 EI 2024年第1期193-204,共12页
A Diesel Particulate Filter(DPF)is a critical device for diesel engine exhaust products treatment.When using active-regeneration purification methods,on the one hand,a spatially irregular gas flow can produce relative... A Diesel Particulate Filter(DPF)is a critical device for diesel engine exhaust products treatment.When using active-regeneration purification methods,on the one hand,a spatially irregular gas flow can produce relatively high local temperatures,potentially resulting in damage to the carrier;On the other hand,the internal temperature field can also undergo significant changes contributing to increase this risk.This study explores the gas flow uniformity in a DPF carrier and the related temperature behavior under drop-to-idle(DTI)condition by means of bench tests.It is shown that the considered silicon carbide carrier exhibits good flow uniformity,with a temperature deviation of no more than 2%with respect to the same radius measurement point at the outlet during the regeneration stage.In the DTI test,the temperature is relatively high within r/2 near the outlet end,where the maximum temperature peak occurs,and the maximum radial temperature gradient is located between r/2 and the edge.Both these quantities grow as the soot load increases,thereby making the risk of carrier burnout greater.Finally,it is shown that the soot load limit of the silicon carbide DPF can be extended to 11 g/L,which reduces the frequency of active regeneration by approximately 40%compared to a cordierite DPF. 展开更多
关键词 DPF flow uniformity DTI silicon carbide carrier soot load
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Spontaneous Abortions in the Second Trimester of Pregnancy: Research and Analysis of Factors Associated at Laquintinie Hospital in Douala
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作者 Henri Essome Moustapha Bilkissou +13 位作者 Merlin Boten Bounyom Sandrine Ngoumi Ingrid Doriane Ofakem Ilick Astrid Ndolo Kondo Fulbert Mangala Nkwele Michel Roger Ekono Alphonse Ngalame Nyong Robert Tchounzou Junie Ngaha Yaneu Marga Vanina Ngono Akam Gervais Mounchikpou Ngouhouo Grâce Tocki Toutou Théophile Nana Njamen Pascal Foumane 《Open Journal of Obstetrics and Gynecology》 2024年第8期1130-1143,共14页
Introduction: Spontaneous abortion of the second trimester is an interruption of pregnancy with complete expulsion or not of the product of conception between 15 and 28 weeks of pregnancy without any maneuvers. The ob... Introduction: Spontaneous abortion of the second trimester is an interruption of pregnancy with complete expulsion or not of the product of conception between 15 and 28 weeks of pregnancy without any maneuvers. The objective of our study was to determine the factors associated with second trimester spontaneous abortions at Laquintinie Hospital in Douala. Methodology for this purpose: We conducted a case-control study from January to May 2019 on pregnant women who may or may not have had spontaneous second trimester abortions. Results: In total we recorded 1609 pregnancies and recruited 184 patients, including 46 cases and 138 controls;which gave a frequency of spontaneous abortion in the second trimester of pregnancy of 2.85%. A correlative analysis showed that spontaneous abortions in the second trimester were associated with housewife status (OR = 2.89;CI = 1.21 - 6.79;p = 0.010), gestation > 5 (OR = 4.09;CI = 1.02 - 17.66;p = 0.040), multiparity (OR = 3.81;CI = 1.59 - 9.16;p = 0.002), history of endouterine maneuvers (OR = 5.64;CI = 2.43 - 13 .03;p = 0.000), malaria in pregnancy (OR = 3.99;CI = 1.1 - 14.76;p = 0.030), incompleteness on the second trimester ultrasound (OR = 2.37;CI = 1.18 - 4.70;p = 0.010), jolts when traveling (OR = 46.04;CI = 17.29 - 123.66;p = 0.000), long car journeys (OR = 7.05;CI = 1.99 - 27.77;p = 0.000). After logistic regression eliminating the confounding factors, only the following were associated with abortions: Multiparity (OR = 13.90;CI = 2.96 - 65.18;p = 0.000), endo uterine maneuvers (OR = 3.69;CI = 1. 01 - 13.44;p = 0.047), jolts when traveling (OR = 72.63;CI = 19.47 - 270.96;p = 0.000), long car journeys (OR = 15.41;CI = 2.7 - 85, 95;p = 0.000). Conclusion: Our study reveals that a set of factors contribute to the occurrence of spontaneous abortions in the second trimester of pregnancy in our context. 展开更多
关键词 Spontaneous Abortion second Trimester Associated Factors Laquintinie
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Hot carrier cooling in lead halide perovskites probed by two-pulse photovoltage correlation spectroscopy
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作者 Yuqing Huang Chaoyu Guo +9 位作者 Lei Gao Wenna Du Haotian Zheng Da Wu Zhengpu Zhao Chu-Wei Zhang Qin Wang Xin-Feng Liu Qingfeng Yan Ying Jiang 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第10期116-119,共4页
The next-generation hot-carrier solar cells,which can overcome the Shockley-Queisser limit by harvesting excessenergy from hot carriers,are receiving increasing attention.Lead halide perovskite(LHP)materials are consi... The next-generation hot-carrier solar cells,which can overcome the Shockley-Queisser limit by harvesting excessenergy from hot carriers,are receiving increasing attention.Lead halide perovskite(LHP)materials are considered aspromising candidates due to their exceptional photovoltaic properties,good stability and low cost.The cooling rate of hotcarriers is a key parameter influencing the performance of hot-carrier solar cells.In this work,we successfully detected hotcarrier dynamics in operando LHP devices using the two-pulse photovoltage correlation technique.To enhance the signalto-noise ratio,we applied the delay-time modulation method instead of the traditional power modulation.This advancementallowed us to detect the intraband hot carrier cooling time for the organic LHP CH_(3)NH_(3)PbBr_(3),which is as short as 0.21 ps.In comparison,the inorganic Cs-based LHP CsPbBr_(3)exhibited a longer cooling time of around 0.59 ps due to differentphonon contributions.These results provide us new insights into the optimal design of hot-carrier solar cells and highlightthe potential of LHP materials in advancing solar cell technology. 展开更多
关键词 two-pulse correlation spectroscopy lead halide perovskites hot carrier cooling ultrafast dynamics
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Understanding the catalytic performance and deactivation behaviour of second-promoter doped Pt/WO_(χ)/γ-Al_(2)O_(3) catalysts in the glycerol hydrogenolysis for selective and cleaner production of 1,3-propanediol
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作者 Rafik Rajjak Shaikh Sittichai Damruang +2 位作者 Rais Ahmad Khan Supareak Praserthdam Piyasan Praserthdam 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第7期486-507,共22页
The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol(1,3-PDO).The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenol-ysis but the ca... The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol(1,3-PDO).The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenol-ysis but the catalyst deactivation via sintering,metal leaching,and coking can predominantly occur in the aqueous phase reaction.In this work,the effect of reaction temperature,pressure and second promoter(Cu,Fe,Rh,Mn,Re,Ru,Ir,Sn,B,and P)on catalytic performance and deactivation behaviour of Pt/WOx/-Al2O3 was investigated.When doped with Rh,Mn,Re,Ru,Ir,B,and P,the second promoter boosts catalytic activity by promoting great dispersion of Pt on support and increasing Pt surface area.The increased Bronsted acid sites lead to selective synthesis of 1,3-PDO than 1,2-propanediol(1,2-PDO).The characterization studies of fresh and spent catalysts reveal that the main cause of catalyst deactivation is the Pt sintering,as interpreted based on XRD,CO chemisorption,and TEM analyses.The Pt sintering is affected depending on the second promoter that can either or reduce the interaction between Pt,WO_(χ)/γ and Al_(2)O_(3).As an electron acceptor of Pt in Pt/WO_(χ)/γ-Al_(2)O_(3),Re and Mn as second promoters resulted in increased Pt^(2+) on the catalytic surface,which strengthens the contact between Pt andγ-Al_(2)O_(3) and WO_(χ),resulting in a decrease in Pt sintering.The metal leaching and coking are not affected by the presence of second promoter.The catalyst modified with a second promoter possesses improved catalytic activity and 1,3-PDO production,however the stability continues to remain a challenge.The present work unrav-elled the determining parameters of catalytic activity and deactivation,thus providing a promising pro-tocol toward effective catalysts for glycerol hydrogenolysis. 展开更多
关键词 Glycerol hydrogenolysis 1 3-PROPANEDIOL Metal-support interaction second promoter Liquid phase Catalyst deactivation
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