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Mesoscale study on explosion-induced formation and thermochemical response of PTFE/Al granular jet

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Defence Technology（防务技术） 2023年第5期23卷 112-125页

作者： Yuan-feng zheng Zhi-jian zheng guan-cheng Lu Hai-fu Wang Huan-guo Guo State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

The dynamic formation,shock-induced inhomogeneous temperature rise and corresponding chemical reaction behaviors of PTFE/Al reactive liner shaped charge jet(RLSCJ)are investigated by the combination of mesoscale simulation,reaction kinetics and chemical energy release test.A two-dimensional granular model is developed with the randomly normal distribution of aluminum particle sizes and the particle delivery ***,the granular model is employed to study the shock-induced thermal behavior during the formation and extension processes of RLSCJ,as well as the temperature history curves of aluminum *** simulation results visualize the motion and temperature responses of the RLSCJ at the grain level,and further indicate that the aluminum particles are more likely to gather in the last two-thirds of the jet along its *** analysis shows that the shock,collision,friction and deformation behaviors are all responsible for the steep temperature rise of the reactive *** addition,a shock-induced chemical reaction extent model of RLSCJ is built based on the combination of the Arrhenius model and the Avrami-Erofeev kinetic model,by which the chemical reaction growth behavior during the formation and extension stages is described *** model indicates the reaction extent highly corresponds to the aluminum particle temperature history at the formation and extension *** last,a manometry chamber and the corresponding energy release model are used together to study the macroscopic chemical energy release characteristics of RLSCJ,by which the reaction extent model is verified.

关键词： Reactive materials Shaped charge Mesoscale simulation Formation Thermochemical response

The interpretation of the CMBR

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Research in Astronomy and Astrophysics 2021年第9期21卷 180-184页

作者： yi-Jia zheng National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

In the popular ACDM model,the cosmic microwave background radiation(CMBR)is thought to be the remnant of the early hot *** important precondition of this interpretation of CMBR is:after the last scattering surface formed,the high temperature ionized gases in the universe became low temperature neutral gases and so the universe has been completely transparent to the radiation which comes from the hot early ***,observations show that today most gases in the universe are still in a high temperature ionized *** universe is not completely transparent to the radiation which comes from the hot early *** to the famous Sunyaev-Zeldovich effect,if the CMBR comes from the early hot universe and follows a perfect blackbody spectrum,the free electrons in the cosmic plasma will distort the perfect blackbody spectrum of the *** this case,the observed CMBR cannot be of a perfect blackbody *** is a fatal flaw in the interpretation of CMBR using the ACDM *** order to overcome this fatal flaw,in this paper it is proposed that in the ACDM model frame,a better interpretation of CMBR is:The CMBR is a thermal equilibrium product between the high temperature ionized gases and the cosmic radiation field in the local universe space.

关键词： cosmology:theory cosmological model cosmic microwave background radiation

Biodegradation,hemocompatibility and covalent bonding mechanism of electrografting polyethylacrylate coating on Mg alloy for cardiovascular stent

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Journal of Materials Science & Technology 2020年第11期42卷 114-126页

作者： Yong-Xin Yang Zhe Fang yi-Hao Liu Ya-Chen Hou Li-Guo Wang yi-Fan Zhou Shi-Jie Zhu Rong-Chang Zeng Yu-Feng zheng Shao-Kang guan School of Materials Science and Engineering Zhengzhou UniversityZhengzhou450001China Henan Key Laboratory of Advanced Magnesium Alloys Zhengzhou450002China Key Laboratory of Advanced Materials Processing&Mold Ministry of Education Zhengzhou450002China Corrosion Laboratory of Light Metals College of Material Science and EngineeringShandong University of Science and TechnologyQingdao266590China State Key Laboratory for Turbulence and Complex System and Department of Materials Science and Engineering College of EngineeringPeking UniversityBeijing100871China

Organic coatings are the most widely employed approach for the promotion of corrosion resistance of magnesium(Mg)***,traditional organic coatings are weakly bonded to Mg substrates due to physical ***,a polyethylacrylate(PEA)coating was fabricated on Mg-Zn-YNd alloy via *** surface structure and chemical composition were characterized by means of scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDS),atomic force microscope(AFM)and Fourier transform infrared(FTIR)as well as time of flight-secondary ion mass spectrometer(To F-SIMS).The results showed that the surface roughness of PEA coating was dominated by scan rate;while the coverage and integrity of PEA coating were mainly affected by the monomer concentration and sweep *** F-SIMS results indicated that PEA coating was wholly covered on Mg alloy,and the presence of C2H3Mg-fragment confirmed the covalent bond between PEA coating and Mg *** addition,DFT calculation results of the adsorption of EA molecules with Mg substrate agree well with the experimental phenomena and observation,suggesting that the electrons in 3s orbit of Mg atoms and 2pz orbit of C1 atom participated in the formation of covalent bond between PEA coating and Mg *** polarization curves and immersion test demonstrated that the PEA coatings could effectively enhance the corrosion resistance of Mg *** platelet adhesion results designated that platelets were barely visible on PEA coating,which implied that PEA coating could effectively prevent the thrombosis and coagulation of *** coating might be a promising candidate coating of Mg alloy for cardiovascular stent.

关键词： Magnesium alloy Organic coating Electro-grafting Covalent bond Density functional theory Biomaterial

Bowel preparation before colonoscopy: Consequences, mechanisms, and treatment of intestinal dysbiosis

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World Journal of Gastroenterology 2025年第2期31卷 13-26页

作者： Ze-Long zheng Qing-Fan zheng Li-Qiang Wang yi Liu Department of Gastroenterology(Endoscopy Center) China-Japan Union Hospital of Jilin UniversityChangchun 130033Jilin ProvinceChina

The term“gut microbiota”primarily refers to the ecological community of various microorganisms in the gut,which constitutes the largest microbial community in the human *** adequate bowel preparation can improve the results of colonoscopy,it may interfere with the gut *** preparation for colonoscopy can lead to transient changes in the gut microbiota,potentially affecting an individual’s health,especially in vulnerable populations,such as patients with inflammatory bowel ***,measures such as oral pro-biotics may ameliorate these adverse *** focused on the bowel prepa-ration-induced changes in the gut microbiota and host health status,hypothesized the factors influencing these changes,and attempted to identify measures that may reduce dysbiosis,thereby providing more information for individualized bowel preparation for colonoscopy in the future.

关键词： Bowel preparation Colonoscopy Microbiota Inflammatory bowel disease Probiotics

Thermal fatigue behavior of K465 superalloy

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Rare Metals 2006年第3期25卷 202-209页

作者： YANG Jinxia zheng Qi SUN Xiaofeng guan Hengrong HU Zhuangqi Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The thermal fatigue behavior of K465 superalloy was investigated at the peak temperature of 1050℃. By scanning electron microscopy （SEM） and optical microscopy, the main crack length was observed and measured. The initiation sites of the tested alloys are different in as-cast （named as K465） and solution heat treatment （named as SK465） conditions. In K465 alloy, most thermal fatigue cracks nucleate at （Nb,W,Ti）C carbides. In SK465 alloy, thermal fatigue cracks initiate in interdendritic regions, MC-type carbides and some interfaces. Thermal fatigue cracks propagate in transdendritic mode, and M6C-type carbides could retard thermal fatigue crack growth for SK465 superalloy.

关键词： K465 superalloy thermal fatigue crack initiation and growth carbides

Chemical renal artery denervation with appropriate phenol in spontaneously hypertensive rats

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Journal of Geriatric Cardiology 2018年第11期15卷 695-702页

作者： Ming WANG Wen-zheng HAN Min ZHANG Wei-yi FANG Xin-Rong ZHAI Shao-Feng guan Xin-Kai QU Department of Cardiology Huadong Hospital Affiliated to Fudan University Shanghai China Shanghai Key Laboratory of Clinical Geriatric Medicine Shanghai China Department of Cardiology Shanghai Chest Hospital Shanghai Jiaotong University Shanghai China

Objective To explore the effectiveness of renal denervation (RDN) on blood pressure with the appropriate dosage of phenol/ethanol solution in spontaneously hypertensive rats (SHRs). Methods RDN was performed on the bilateral renal artery. Forty SHRs were divided into four groups according on the dosage of phenol (10% phenol in absolute ethanol): sham group, 0.5 mL phenol group, 1 mL phenol group and 1.5 mL phenol group (n = 10 in each group). Blood pressure was measured by tail-cuff plethysmography. Plasma creatinine was determined four weeks after the treatment. The kidneys and renal arteries were collected and processed for histological examination. Results A sustained decrease in systolic blood pressure (SBP) was only observed after the application of 1 mL phenol for four weeks, while SBP was lowered during the first week after RDN and increased in the following three weeks in the 0.5 mL and 1.5 mL phenol groups compared with the sham group. Renal norepinephrine (NE) was significantly decreased four weeks after RDN in the 1 mL and 1.5 mL phenol group compared with the sham group, but not in the 0.5 ml group. RDN with 1 mL phenol obviously reduced glomerular fibrosis. Histopathological analysis showed that tyrosine hydroxylase immunoreactivity was lower in the 1 mL and 1.5 mL phenol groups compared with the sham group. Moderate renal artery damage occurred in the 1.5 mL phenol group. Conclusion Chemical denervation with 1 ml phenol (10% phenol in absolute ethanol) effectively and safely damaged peripheral renal sympathetic nerves and contributed to the sustained reduction of blood pressure in SHRs.

关键词： Hypertension Norepinephrine Phenol Renal denervation Spontaneously hypertensive rats

Numerical modeling of regional groundwater flow in the Heihe River Basin,China:Advances and new insights

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Science China Earth Sciences 2015年第1期58卷 3-15页

作者： YAO yingying zheng ChunMiao TIAN Yong LIU Jie zheng yi Center for Water Research College of EngineeringPeking University Department of Geological Sciences University of Alabama

Numerical groundwater modeling is an effective tool to guide water resources management and explore complex groundwater-dependent ecosystems in arid *** the Heihe River Basin(HRB),China’s second largest inland river basin located in arid northwest China,a series of groundwater flow models have been developed for those purposes over the past 20 *** models have elucidated the characteristics of groundwater flow systems and provided the scientific basis for a more sustainable management of groundwater resources and ecosystem *** first part of this paper presents an overview of previous groundwater modeling studies and key lessons learned based on seven different groundwater models in the middle and lower HRB at sub-basin *** second part reviews the rationale for development of a regional basin-scale groundwater flow model that unifies previous sub-basin *** addition,this paper discusses the opportunities and challenges in developing a regional groundwater flow model in an arid river basin such as the HRB.

关键词： Heihe River Basin groundwater flow modeling regional hydrogeology sustainable groundwater management ecohy-drology

Contrasting the Skills and Biases of Deterministic Predictions for the Two Types of El Nio

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Advances in Atmospheric Sciences 2017年第12期34卷 1395-1403页

作者： Fei zheng Jin-yi YU International Center for Climate and Environment Science Institute of Atmospheric PhysicsChinese Academy of Sciences Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Department of Earth System Science University of California

The tropical Pacific has begun to experience a new type of El Nio, which has occurred particularly frequently during the last decade, referred to as the central Pacific(CP) El Nio. Various coupled models with different degrees of complexity have been used to make real-time El Nio predictions, but high uncertainty still exists in their forecasts. It remains unknown as to how much of this uncertainty is specifically related to the new CP-type El Nio and how much is common to both this type and the conventional Eastern Pacific(EP)-type El Nio. In this study, the deterministic performance of an El Nio–Southern Oscillation(ENSO) ensemble prediction system is examined for the two types of El Nio. Ensemble hindcasts are run for the nine EP El Nio events and twelve CP El Nio events that have occurred since 1950. The results show that(1) the skill scores for the EP events are significantly better than those for the CP events, at all lead times;(2) the systematic forecast biases come mostly from the prediction of the CP events; and(3) the systematic error is characterized by an overly warm eastern Pacific during the spring season, indicating a stronger spring prediction barrier for the CP El Nio. Further improvements to coupled atmosphere–ocean models in terms of CP El Nio prediction should be recognized as a key and high-priority task for the climate prediction community.

关键词： ENSO EP El Nio CP El Nio prediction skill systematic bias spring prediction barrier

Generating femtosecond coherent X-ray pulses in a diffractionlimited storage ring with the echo-enabled harmonic generation scheme

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Nuclear Science and Techniques 2018年第10期29卷 191-199页

作者： Wei-Hang Liu guan-Qun Zhou yi Jiao Key Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 10004China University of Chinese Academy of Sciences Beijing 100049China

To study ultrafast processes at the sub-picosecond level, novel methods based on coherent harmonic generation technologies have been proposed to generate ultrashort radiation pulses in existing ring-based light sources. Using the High Energy Photon Source as an example, we numerically test the feasibility of implementing one coherent harmonic generation technology, i.e.,the echo-enabled harmonic generation(EEHG) scheme, in a diffraction-limited storage ring(DLSR). Two different EEHG element layouts are considered, and the effect of the EEHG process on the electron beam quality is also analyzed. Studies suggest that soft X-ray pulses, with pulse lengths of a few femtoseconds and peak powers of up to1 MW, can be generated by using the EEHG scheme, while causing little perturbation to the regular operation of a DLSR.

关键词： Echo-enabled harmonic generation Diffraction-limited storage ring High-energy photon source Femtosecond X-ray pulses