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Pre-chamber turbulent jet ignition of methane/air mixtures with multiple orifices in a large bore constant volume chamber: effect of air-fuel equivalence ratio and pre-mixed pressure

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Frontiers in Energy 2019年第3期13卷 483-493页

作者： Xiang li Wenzheng ZHANG Zhong HUANG Dehao JU li HUANG Mingzhi feng Xingcai LU Zhen HUANG Key Laboratory of Power Machinery and Engineering Ministry of EducationShanghai Jiao Tong UniversityShanghai 200240China Shanghai Marine Diesel Engine Research Institute Shanghai 201108China

liquefied natural gas (LNG), mainly composed of methane, is in progress to substitute diesel fuel in heavyduty marine engine for practical, economic, and environmental considerations. However, natural gas is relatively difficult to be ignited in a large bore combustion chamber. A combustion enhancement technique called prechamber turbulent jet ignition (TJI) can permit combustion and flame propagation in a largebore volume. To investigate the effect of air-fuel equivalence ratio and pre-mixed pressure on pre-chamber TJI of methane/air mixtures with multiple orifices in a large bore volume, experimental tests and computational simulations were implemented to study the discharge of hot turbulent jets from six orifices of the pre-chamber. Different initial pressures and air-fuel equivalence ratios were considered to analyze the characteristics of TJI. The asymmetry of the turbulent jet actuated from six different orifices were found due to the asymmetric orientation of the spark plug, resulting in the inhomogeneous distribution of combustion in the constant volume chamber, which should be considered seriously in the marine engine design. Besides,as the premixed pressure increases, it has more effect on the flame propagation and plays a more important role, as it further increases.

关键词： marine engine natural gas methane turbulent jet ignition (TJI) pre-chamber

Proton-induced Conversion from Non-Aufbau to Aufbau Electronic Structure of an Organic Radical with Turn-on Fluorescence

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Chemical Research in Chinese Universities 2022年第3期38卷 798-802页

作者： CHEN Zhangwu Li Feng State Key Laboratory of Supramolecular Structure and Materials College of ChemistryJilin UniversityChangchun130012P.R.China

We report a donor-acceptor(D-A)type non-luminescent neutral radical,tris-2,4,6-trichlorophenylmethyl-N,N-dimethyl-9H-carbazol-3-amine(TTM-Cz-DMA).The results of cyclic voltammetry and quantum chemistry calculation confirm TTM-Cz-DMA has the non-Aufbau electronic structure,which means the singly occupied molecular orbital(SOMO)lies below the highest doubly occupied molecular orbital(HOMO).The non-Aufbau electronic structure changes to the Aufbau electronic structure after protonation and exhibits proton-responsive turn-on fluorescence,which is totally reversible by deprotonation.The dihedral angle between donor and acceptor moieties of TTM-Cz-DMA in excited state reduces from 88°to 62°after protonation,causing the turn-on fluorescence.Our results offer a viewing angle to understand the luminescence of radicals and provide a possible application of proton detection.

关键词： Luminescent radical Singly occupied molecular orbital(SOMO)-highest doubly occupied molecular orbital(HOMO)conversion Non-Aufbau Turn-on fluorescence

Cistanche Deserticola for Regulation of Bone Metabolism:Therapeutic Potential and Molecular Mechanisms on Postmenopausal Osteoporosis

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Chinese Journal of Integrative Medicine 2023年第1期29卷 74-80页

作者： WANG Cheng Li Feng li Yang feng Hui ZHAO Min-wei TU Peng-fei TIAN Hua Department of Orthopaedics/Engineering Research Center of Bone and Joint Precision Medicine/Beijing Key Laboratory of Spinal Disease Research Peking University Third HospitalBeijing100191China Peking University School of Pharmaceutical Sciences Beijing100191China

Osteoporosis is a generalized disease of bone that leads to a loss of bone density and bone mass,destruction of bone microstructure,increased brittleness and therefore fracture.At present,the main treatment of Western medicine is drug therapy such as bisphosphonates,calcitriol,vitamin D,etc.However,long-term use of these drugs may bring some adverse reactions.Chinese herbal medicine Cistanche deserticola could regulate bone metabolism by promoting osteoblast activity and inhibiting osteoclast activity with low toxicity and adverse reactions.Therefore,Cistanche deserticola has attracted increasing attention for its efficacy in the prevention and treatment of osteoporosis in recent years.Here we present a literature review of the molecular pathways involved in osteoporosis and the effects of Cistanche deserticola on bone metabolism.Our objective is to clarify the mechanism of Cistanche deserticola in the treatment of osteoporosis.

关键词： osteoporosis Cistanche deserticola bone metabolism Chinese medicine

Seed size affects rodent–seed interaction consistently across plant species but not within species:evidence from a seed tracking experiment of 41 tree species

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Integrative Zoology 2022年第5期17卷 930-943页

作者： Si CHEN Li Feng Bo WANG School of Resources and Environmental Engineering Anhui UniversityHefeiAnhui ProvinceChina Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMenglaYunnan ProvinceChina Ailaoshan Station of Subtropical Forest Ecosystem Studies Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesJingdongYunnan ProvinceChina Anhui Province Key Laboratory of Wetland Ecosystem Protection and Restoration(Anhui University) HefeiAnhui ProvinceChina

Scatter-hoarding rodents play a crucial role in seed survival and seed dispersal.As one of the most important seed traits,seed size and its effect on rodent–seed interaction attract lots of attention.Current studies usually target one or a few species and show inconsistent patterns;however,few experiments include a large number of species although many plant species usually coexist in natural forest and overlap in fruiting time.Here,we tracked the dispersal and predation of 26100 seeds belonging to 41 tree species in a subtropical forest for 2 years.Most species showed no relationships between seed size and rodent foraging preference,while the remaining species displayed diverse of patterns:monotonic decrease and increase trends,and hump-shaped and U-shaped patterns,indicating that a one-off study with a few species might give misleading information.However,the seed size effect across species was consistent in both years,indicating that including a large number of species that hold a sufﬁcient range of seed size may avoid the aforementioned bias.Interestingly,seed size effect differed among rodent foraging processes:a negative effect on seed harvest,a hump-shaped effect on seed removal and removal distance,while a positive effect on overwinter survival of cached seeds,indicating that rodents may make trade-offs between large and small seeds both among foraging processes and within a single process,thus lead to a parabolic relationship between seed size and seed dispersal success,that is medium-sized seeds were more likely to be removed and cached,and transported with a further distance.

关键词： foraging preference plant–animal interaction scatter-hoarding seed dispersal seed predation

Stable Near-infrared-emitting Radical Nanoparticles for Fluorescence Imaging

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Chemical Research in Chinese Universities 2023年第2期39卷 192-196页

作者： li Xinru TAN Wenjia BAI Xuemei Li Feng State Key Laboratory of Supramolecular Structure and Materials College of ChemistryJilin UniversityChangchun130012P.R.China China-Japan Union Hospital of Jilin University Changchun130033P.R.China

Stable neutral luminescent radicals with unpaired electrons exhibit unique spin-allowed doublet-doublet transitions,which has attracted significant attention.Although they are pure organic molecules without metal ions thus thought to have low biological toxicity,the application of luminescent radicals to bioimaging has rarely been reported.Here,a stable radical with efficient near-infrared(NIR)emission and good photostability was designed and synthesized.After being wrapped into nanoparticles,it was applied to cell fluorescence imaging.The cytotoxicity experiments suggested that the nanoparticles have remarkable biocompatibility and excellent stability.An NIR fluorescent signal was successfully observed in the cytoplasm of HCT116 cells.The experimental results gave the first example of NIR emitting radical nanoparticles for cell fluorescence imaging and proved the feasibility of the application of luminescent radicals to fluorescence imaging.

关键词： Fluorescence imaging Near-infrared emission Radical Luminescent radical Doublet emission

A Random Fusion of Mix 3D and Polar Mix to Improve Semantic Segmentation Performance in 3D lidar Point Cloud

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Computer Modeling in Engineering & Sciences 2024年第7期140卷 845-862页

作者： Bo liu Li Feng Yufeng Chen School of Computer Science and Engineering Macao University of Science and TechnologyMacao999078China School of Computer Science and Artificial Intelligence Chaohu UniversityChaohu238000China Institute of Vehicle Information Control and Network Technology Hubei University of Automotive TechnologyShiyan442002China

This paper focuses on the effective utilization of data augmentation techniques for 3Dlidar point clouds to enhance the performance of neural network models.These point clouds,which represent spatial information through a collection of 3D coordinates,have found wide-ranging applications.Data augmentation has emerged as a potent solution to the challenges posed by limited labeled data and the need to enhance model generalization capabilities.Much of the existing research is devoted to crafting novel data augmentation methods specifically for 3D lidar point clouds.However,there has been a lack of focus on making the most of the numerous existing augmentation techniques.Addressing this deficiency,this research investigates the possibility of combining two fundamental data augmentation strategies.The paper introduces PolarMix andMix3D,two commonly employed augmentation techniques,and presents a new approach,named RandomFusion.Instead of using a fixed or predetermined combination of augmentation methods,RandomFusion randomly chooses one method from a pool of options for each instance or sample.This innovative data augmentation technique randomly augments each point in the point cloud with either PolarMix or Mix3D.The crux of this strategy is the random choice between PolarMix and Mix3Dfor the augmentation of each point within the point cloud data set.The results of the experiments conducted validate the efficacy of the RandomFusion strategy in enhancing the performance of neural network models for 3D lidar point cloud semantic segmentation tasks.This is achieved without compromising computational efficiency.By examining the potential of merging different augmentation techniques,the research contributes significantly to a more comprehensive understanding of how to utilize existing augmentation methods for 3D lidar point clouds.RandomFusion data augmentation technique offers a simple yet effective method to leverage the diversity of augmentation techniques and boost the robustness of models.The insights gained from this

关键词： 3D lidar point cloud data augmentation RandomFusion semantic segmentation

Splash Zone Dynamic Analysis of A Suspended Semi-Submerged Subsea Module for Irregular Waves

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China Ocean Engineering 2023年第2期37卷 258-271页

作者： ZAN Ying-fei GUO Rui-nan Li Feng liU Pei-lin HUANG Fu-xiang TIAN li-feng College of Shipbuilding Engineering Harbin Engineering UniversityHarbin 150001China Offshore Oil Engineering Co. Ltd.Tianjin 300451China

Experimental and numerical studies on the dynamic cable tension of a subsea module during semi-submerged hoisting tests are performed. The experiments are carried out in irregular waves and the time-domain numerical simulations are conducted using the software “Simulation of Marine Operations”. The numerical formulation is validated through a comparison with experimental test measurements. The effects of the significant wave height, spectral peak period,and wave direction on the dynamic effect in the main sling and sub-slings are then investigated numerically. The relationship between the wave parameters and the dynamic effect is identified in the time and frequency domains,enabling the allowable sea states to be partially specified. The extreme dynamic effects in all slings under different wave conditions are estimated by using cumulative distribution functions of the Gumbel distribution. The results show that it is reasonable to model a complex subsea module via slender elements and depth-dependent coefficients in simulations of offshore operations. Lowering operations are safer if the wave height is 1 m and the wave period is larger than 8 s because the wave steepness is sufficient for the maximum possible dynamic effect to remain below 0.9. The dynamic tension may decrease when the wave direction is approximately 150°. It is dangerous for subsea modules to encounter lateral waves while entering the water because large overloads and underloads in the extreme dynamic tension may cause snap loads to occur and the slings to become slack.

关键词： splash zone subsea module cavity shell time-domain simulation dynamic effect

Dynamical Behavior of SEIR-SVS Epidemic Models with Nonlinear Incidence and Vaccination

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Acta Mathematicae Applicatae Sinica 2022年第2期38卷 282-303页

作者： Xiao-mei feng li-li liU feng-qin ZHANG School of Mathematics and Informational Technology Yuncheng UniversityYuncheng 044000China School of Mathematics and Informational Sciences Shaanxi Normal UniversityXi'an 710062China Complex Systems Research Center Shanxi UniversityTaiyuan 030006China Shanxi Key Laboratory of Mathematical Techniques and Big Data Analysis on Disease Control and Prevention Shanxi UniversityTaiyuan 030006China

For some infectious diseases such as mumps,HBV,there is evidence showing that vaccinated individuals always lose their immunity at different rates depending on the inoculation time.In this paper,we propose an age-structured epidemic model using a step function to describe the rate at which vaccinated individuals lose immunity and reduce the age-structured epidemic model to the delay differential model.For the age-structured model,we consider the positivity,boundedness,and compactness of the semiflow and study global stability of equilibria by constructing appropriate Lyapunov functionals.Moreover,for the reduced delay differential equation model,we study the existence of the endemic equilibrium and prove the global stability of equilibria.Finally,some numerical simulations are provided to support our theoretical results and a brief discussion is given.

关键词： vaccination age-structured epidemic model delay differential equation model stability Lyapunov functional

A case report of multimodal ultrasound imaging in the diagnosis of giant retroperitoneal ganglioneuroma

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Cancer Innovation 2023年第5期2卷 433-437页

作者： Li Feng Yong Wang Department of Ultrasound National Cancer CenterNational Clinical Research Center for CancerCancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingChina

Retroperitoneal ganglioneuroma is a rare benign tumor that is challenging in terms of clinical diagnosis.Computed tomography and magnetic resonance imaging are usually performed for diagnosis rather than convenient and inexpensive ultrasonography.Here,we present the case of a 21‐year‐old female patient who was diagnosed by multimodal ultrasound imaging and whose diagnosis was confirmed by ultrasound‐guided core needle biopsy before surgery.We hope that this rare case will help clinicians and radiologists realize the advantages of multimodal ultrasound imaging in the diagnosis of retropeitoneal solid tumors,and reduce misdiagnosis.

关键词： diagnosis ganglioneuroma retroperitoneal mass ultrasonography