Numerical Simulation on Characteristics of Debris Clouds Produced by Conical Projectiles Hypervelocity Impact on Thin Plates

Xun Liu,Fangfang Gai,Su Cheng 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.6

With the unceasing development of space activity, the total number of space debris is ever increasing, which greatly threatens orbiting space vehicles. To research the characteristics of debris clouds which are produced by conical projectiles hypervelocity impact on thin plates, SPH (smoothed particle hydrodynamics) methods in AUTODYN is used. Characteristics of debris cloud produced by conical projectiles with different ratio between length and diameter hypervelocity impact on thin plates are investigated with the same mass and velocity by numerical simulation. Effects of the ratio between length and diameter of the projectiles affecting on the form of debris cloud, axial location of debris clouds, radial extension of debris cloud and tip particle velocity of debris cloud are obtained. It is shown that the degree of fragmentation of the projectiles and debris cloud diffusion is changed with the velocity of the projectiles, the ratio between length and diameter and the impacting direction. The increasing ratio between length and diameter of projectiles can reduce the damage of thin plates but rise the damage of the wall of spacecraft by the debris clouds impact on with the same mass and velocity.

Numerical Simulation on Crater Characteristics of Different Shape of Projectiles Hypervelocity Impact on Thick Plates

Liu Xun,Gai Fangfang 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.2

Hypervelocity impact by space debris can cause direct damage to spacecraft internal subsystem, and even lead to catastrophic failure of manned spacecraft. To research the crater characteristics of different shape of projectiles hypervelocity impact on semi infinite thick aluminum alloy plates, Lagrange and SPH (smoothed particle hydrodynamics) coupling method in AUTODYN is used. By analyzing the influence on crater characteristics by different impact velocity of spherical projectile, different ratio between length and diameter and different impact velocity of cylindrical projectile, we obtain the law of crater characteristics of the semi infinite thick plates. The research results have reference value and engineering application of guiding significance to the study of spacecraft space debris shield structure design.

Quantitative Evaluation Index for Analysis of Assembly Effect on Shield Tunnel Segment Structures

Xun Liu,Kun Feng,Chuan He,Haihua Zhang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9

The local force and deformation of shield tunnel will be transferred and redistributed owing to the discontinuous segmental structure. This study develops quantitative evaluation index to explore the influence of the axial compression ratio, eccentricity, and longitudinal force on the assembly effect. A full-scale test is conducted on a single segment and staggered assembled segmental linings. First, the results show that the assembly effect has an obvious redistribution influence on the force and deformation of the segment. Second, the influence of eccentricity on the bending moment is much larger than that of the axial force. The stiffness between rings varied at different positions and the larger the stiffness difference, the more obvious the assembly effect. The results demonstrate that the design and mechanical performance of the shield tunnel under different embedded conditions can be optimized by increasing the longitudinal force, which moderates the assembly effect and ensures the structure reaches the highest bearing capacity.

Synthesis of Thermoresponsive Hyperbranched Polyamidoamine and the Molecular Weight, pH, and Anion Sensitive Thermoresponsive Properties Thereof

Yi Liu,Yu Chen,Xun-Yong Liu,Hua-Ji Liu,Fa Cheng 한국고분자학회 2012 Macromolecular Research Vol.20 No.6

Hyperbranched polyamidoamine (HPAMAM) polymers, chemically analogous to the commercially available PAMAM dendrimer, were modified with isobutyric anhydride to result in isobutyramide (IBAm) terminated HPAMAMs (HPAMAM-IBAm). The aqueous solutions of HPAMAM-IBAm polymers had the lower critical solution temperature (LCST). The lower molecular-weight HPAMAM-IBAm exhibited higher LCST and the LCST difference was around 18 oC for one pseudo-generation variation. Further, the hyperbranched thermoresponsive polymers exhibited much lower LCSTs than the corresponding dendrimers with similar molecular weight. The LCST of HPAMAM-IBAm was pH sensitive. At pH below 10, the LCST increased significantly upon decreasing the pH,whereas, at pH above 10, the LCST decreased slowly with an increasing pH value. Nine sodium salts were used to measure the anion effect on the LCST of HPAMAM-IBAm. It was found that the LCST could also be modulated up or down in a broad range by simply adding a small amount of different kinds of inorganic anions. The specific ranking of inorganic anions in salting-out HPAMAM4-IBAm polymer was in accordance with the well-known Hofmeister series.

2018 평창 동계 올림픽의 지역경제 파급효과 실증분석

류천훈(Liu Qian-Xun),강주훈(Kang Joo-Hoon),배주한(Bae Joo-Han) 한국관광레저학회 2013 관광레저연구 Vol.25 No.1

A Weibo Topic Tracking System based on K-means

Yun Liu,Kun-Peng Xia,Jian-Xun Zhao 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.6

This article studied weibo text representation. For the weibo features such as short, real-time, colloquialism and originality, in the original vector space model, we propose a suitable method for weibo text representation. Make all the content words as feature words after participation. And we proposed T-TFIDF weight calculation method according to the features of weibo. According to the vector space model, we proposed a weibo adaptive topic tracking methods based on K-means clustering. Simulation analysis shows that, the method can by comparing the similarity micro-blog and sub topic vector set, determine whether weibo belonging to the topic.

Agglomeration of particles during coal combustion in multistage spouted fluidized tower

Jia-Xun Liu,Jian-Min Gao,Xiao-Feng Wang,Shao-Hua Wu,Ji-Hui Gao 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.3

An experimental platform of spray agglomeration has been designed and built for removing small fly ash particles (PM10) from coal combustion. Systematic experiments were conducted in a multistage spouted tower using kinds of agglomerant solutions. The particle concentration increases greatly from the first stage to the second stage of the tower. With the increase of flue gas flow rate the oscillation of impulse signal response curves increases and the internal circulation of the tower intensifies. The influencing factors such as the surfactant, PH value, flow rate of the agglomerant solutions and inlet flue gas temperature were analyzed. SEM was used to analyze the microstructure of the particles. Final results indicate that the special shape of a multistage spouted fluidized tower has significant influences on the effect of agglomeration. The findings from this work will be helpful to form the basis, and provide guidance for, further studies on the control of fine particles such as PM2.5 or even smaller.

The complete mitochondrial genome of Hemigrapsus sinensis (Brachyura, Grapsoidea, Varunidae) and its phylogenetic position within Grapsoidea

Jin Xun,Guo Xingle,Chen Jian,Li Jiasheng,Zhang Shufei,Zheng Sixu,Wang Yunpeng,Peng Ying,Zhang Kun,Liu Yifan,Liu Bingjian 한국유전학회 2023 Genes & Genomics Vol.45 No.3

Background In this study, the complete mitogenome of Hemigrapsus sinensis was the first identified and analyzed. Objective The complete mitochondrial genome of Hemigrapsus sinensis (Brachyura, Grapsoidea, Varunidae) and its phylogenetic position within Grapsoidea. Methods The sample of Hemigrapsus sinensis was collected and DNA was extracted. After sequencing, NOVOPlasty was used for sequence assembly. Annotate sequences with MITOS WebServer, tRNAscan-SE2.0, and NCBI database. MEGA was used for sequence analysis and Phylosuite was used for phylogenetic tree construction. DnaSP was used to calculate Ka/Ks. Results This mitochondrial genome shows that it was 15,900 bp and encoded 13 PCGs, 22 tRNA genes, two rRNA genes, and one control region. The genome composition tends to A + T (74.34%) and presents a negative GC-skew (− 0.22) and AT-skew (− 0.03). The PCGs initiation codon was the typical ATN and termination codon was the typical TAN, incomplete T or missing. The ML and BI trees showed that H. sinensis was most closely related to Hemigrapsus and clustered together with the Varunidae. And our phylogenetic trees provide proof that Ocypodoidea and Grapsoidea may be of common origin. Meanwhile, in the phylogenetic tree, parallel mixing of Chiromantes and Orisarma raised doubts over the traditional classification system. Besides, Incomplete Lineage sorting (ILS) was observed in Varunidae. In the subsequent analysis of evolution rate, we found that all of the PCGs (NAD4 was not calculated) had undergone negative selections, indicating the conservation of mitochondrial genes of H. sinensis during the evolution. Conclusion Therefore, researching the complete mitogenome of H. sinensis would be contributing to molecular taxonomy, phylogenetic relationship, and breeding optimization within the Grapsoidea superfamily.

Silencing of long noncoding RNA PVT1 inhibits podocyte damage and apoptosis in diabetic nephropathy by upregulating FOXA1

Dong-Wei Liu,Jia-Hui Zhang,Feng-Xun Liu,Xu-Tong Wang,Shao-Kang Pan,Deng-Ke Jiang,Zi-Hao Zhao,Zhang-Suo Liu 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

The number of patients with diabetic nephropathy (DN) is still on the rise worldwide, and this requires the development of new therapeutic strategies. Recent reports have highlighted genetic factors in the treatment of DN. Herein, we aimed to study the roles of long noncoding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1) and histone 3 lysine 27 trimethylation (H3K27me3) in DN. A model of DN was established by inducing diabetes in mice with streptozotocin. Mouse podocyte clone 5 (MPC5) podocytes and primary podocytes were cultured in normal and high glucose media to observe cell morphology and to quantify PVT1 expression. The roles of PVT1 and enhancer of zeste homolog 2 (EZH2) were validated via loss-of-function and gain-of-function in vitro experiments to identify the interactions among PVT1, EZH2, and forkhead box A1 (FOXA1). The podocyte damage and apoptosis due to PVT1 and FOXA1 were verified with in vivo experiments. PVT1 was highly expressed in MPC5 and primary podocytes in DN patients and in cultures grown in high glucose medium. A large number of CpG (C-phosphate-G) island sites were predicted at the FOXA1 promoter region, where PVT1 recruited EZH2 to promote the recruitment of H3K27me3. The silencing of PVT1 or the overexpression of FOXA1 relieved the damage and inhibited the apoptosis of podocytes in DN, as was evidenced by the upregulated expression of synaptopodin and podocin, higher expression of Bcl-2, and lower expression of Bax and cleaved caspase-3. The key findings of this study collectively indicate that the suppression of lncRNA PVT1 exerts inhibitory effects on podocyte damage and apoptosis via FOXA1 in DN, which is of clinical significance.

Nanotwinned Microstructure Engineering of Electroplated Copper for Enhanced Anti-corrosion in Alkaline Medium

Xing‑Quan Liu,Zhe Li,Zhen‑Jia Peng,Rui‑Xun Wang,Zhi‑Quan Liu 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.1

Electroplated copper is a key electronic interconnect material in integrated circuits and printed circuits and inevitablyexposed to corrosive media in manufacturing processes. The present work reports, for the first time, that corrosion resistanceof electroplated copper in 4 wt% NaOH is enhanced via nanotwinned microstructure engineering. Nucleation and growthof oxide/hydroxide on nanotwinned copper are inhibited, attributed to existence of highly (111)-preferred grain orientationand high-density parallelly-aligned coherent twin boundaries at surface. This study unveils a novel anti-corrosion strategyof nantowinned microstructure engineering against alkaline etchant, and exhibits great application values in industrial electroplatingof copper, silver, or their alloys.