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Counterintuitive Ballistic and directional Liquid Transport on a Flexible Droplet Rectifier

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Research 2020年第1期2020卷 1009-1019页

作者： Lei Wang Jing Li Bo Zhang Shile Feng Mei Zhang Dong Wu Yang Lu Ji Jung Kai Jing Liu Zuankai Wang Lei Jiang Beijing Key Lab of Cryo-Biomedical Engineering and Key Lab of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China Department of Mechanical Engineering City University of Hong KongHong Kong 999077China Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education School of ChemistryBeijing Advanced Innovation Center for Biomedical EngineeringBeihang UniversityBeijing 100191China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Precision Machinery and Precision InstrumentationUniversity of Science and Technology of ChinaHefeiAnhui 230027China

Achieving the directional and long-range droplet transport on solid surfaces is widely preferred for many practical applications but has proven to be challenging.Particularly,directionality and transport distance of droplets on hydrophobic surfaces are mutually exclusive.Here,we report that drain fly,a ubiquitous insect maintaining nonwetting property even in very high humidity,develops a unique ballistic droplet transport mechanism to meet these demanding challenges.The drain fly serves as a flexible rectifier to allow for a directional and long-range propagation as well as self-removal of a droplet,thus suppressing unwanted liquid flooding.Further investigation reveals that this phenomenon is owing to the synergistic conjunction of multiscale roughness,structural periodicity,and flexibility,which rectifies the random and localized droplet nucleation(nanoscale and microscale)into a directed and global migration(millimeter-scale).The mechanism we have identified opens up a new approach toward the design of artificial rectifiers for broad applications.

关键词： directional mechanism roughness

directional quantum random walk induced by coherence

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Frontiers of physics 2020年第2期15卷 13-25页

作者： Jin-Fu Chen Yu-Han Ma Chang-Pu Sun Beijing Computational Science Research Center Beijing 100193China Graduate School of China Academy of Engineering Physics No.10 Xibeiwang East RoadHaidian DistrictBeijing 100193China

Quantum walk (QW), which is considered as the quantum counterpart of the classical random walk (CRW), is actually the quantum extension of CRW from the single-coin interpretation. The sequential unitary evolution engenders correlation between different steps in QW and leads to a non-binomial position distribution. In this paper, we propose an alternative quantum extension of CRW from the ensemble interpretation, named quantum random walk (QRW), where the walker has many unrelated coins, modeled as two-level systems, initially prepared in the same state. We calculate the walker's position distribution in QRW for different initial coin states with the coin operator chosen as Hadamard matrix. In one-dimensional case, the walker's position is the asymmetric binomial distribution. We further demonstrate that in QRW, coherence leads the walker to perform directional movement. For an initially decoherenced coin state, the walker's position distribution is exactly the same as that of CRW. Moreover, we study QRW in 2D lattice, where the coherence plays a more diversified role in the walker's position distribution.

关键词： quantum walk random walk ensemble interpretation directional walking coherence

directional growth of Al-Mg_2Si eutectic alloy in the SZ2 unmanned spaceship

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Science China(Physics,Mechanics & Astronomy) 2003年第2期46卷 158-163页

作者：潘明祥李顺朴赵德乾汪卫华闻平俞育德聂玉昕赵生旭庄艳歆陈熙琛 Institute of Physics Extreme Conditions Physics Key Laboratory & Center for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100080China

This paper reports the investigation results on directional growth of Al-Mg2Si eutectic alloy in the SZ2 unmanned spaceship. The analysis shows that microgravity has influence on the directional growth of Al-Mg2Si eutectic alloy. The eutectic colony in space-grown sample is larger than that in ground-grown sample, and the directional effect is not so good as that of terrestrial sample. But there is no obvious difference in the lamellar thickness between these samples, and lamellar interspacing in space sample is smaller than that grown on the ground. A simple discussion is done on the gravity effect on the directional growth of Al-Mg2Si eutectic alloy.

关键词： microgravity, eutectic, directional growth.

directional solidification casting technology of heavy-duty gas turbine blade with liquid metal cooling(LMC) process

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China Foundry 2019年第1期16卷 23-30页

作者： Xiao-fu Liu Yan-chun Lou Bo Yu Gui-qiao Su Chang-chun Li Xin-li Guo Biao Li Guo-yan Shui State Key Laboratory of Light Alloy Casting Technology for High-end Equipment Shenyang Research Institute of Foundry Co.Ltd.Shenyang 110022China

In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of heavy-duty gas turbine with the liquid metal cooling(LMC) process, were studied through the method of microstructure analysis combining. The results show that the ceramic shell with medium strength(the high temperature flexural strength is 8 MPa, the flexural strength after thermal shock resistance is 12 MPa and the residual flexural strength is 20 MPa) can prevent the rupture and runout of the blade. The appropriate temperature(1,520 ℃ for upper region and 1,500 ℃ for lower region) of the heating furnace can eliminate the wide-angle grain boundary, the deviation of grain and the run-out caused by the shell crack. The holding time after pouring(3-5 min) can promote the growth of competitive grains and avoid a great deviation of columnar grains along the crystal orientation , resulting in a straight and uniform grain structure. In addition, to avoid the formation of wrinkles and to ensure a smooth blade surface, the withdrawal rate should be no greater than the growth rate of grain. It is also found that the dendritic space of the blade decreases with the rise of solidification rate, and increases with the enlarging distance between the solidification position and the chill plate.

关键词： liquid metal cooling (LMC) heavy-duty gas turbine large-size blade directional solidification microstructure

Empirical Evidence for the Look-Ahead Behavior of Pedestrians in Bi-directional Flows

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Chinese Physics Letters 2012年第6期29卷 299-302页

作者：郭仁拥黄仕进夏银华黄海军林兴强 CHOI Keechoo College of Computer Science Inner Mongolia UniversityHohhot 010021 Department of Civil Engineering The University of Hong KongPokfulam RoadHong Kong Department of Mathematics University of Science and Technology of ChinaHefei 230026 School of Economics and Management Beijing University of Aeronautics and AstronauticsBeijing 100191 Department of Civil and Structural Engineering The Hong Kong Polytechnic UniversityHong Kong Department of Transportation Engineering Ajou UniversitySan 5 Woncheon-DongYeongtong-KuSuwon442-749 Korea

Using the sample data obtained from a group of pedestrian experiments,a function formulating the velocitydensity relationship of pedestrians and linear regression is proposed to provide empirical evidence for the lookahead behavior of pedestrians in bi-directional flows.We find that the velocity of pedestrians is negatively correlated with not only the densities of the opposite-direction and the identical-direction pedestrians around them but also the densities of the same-direction pedestrians ahead of them.Moreover,the movement of pedestrians is most affected by other pedestrians moving in the same direction about 1 m ahead.

关键词： directional identical ahead

Microstructure evolution in grey cast iron during directional solidification

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International Journal of Minerals,Metallurgy and Materials 2017年第8期24卷 884-890页

作者： Xian-fei Ding Xiao-zheng Li Qiang Feng Warkentin Matthias Shi-yao Huang National Center for Materials Service Safety University of Science and Technology Beijing Beijing Key Laboratory of Special Melting and Preparation of High-end Metal University of Science and Technology Beijing State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Ford Research & Advanced Engineering Europe Materials and Process Research Ford Motor Research and Engineering Center

The solidification characteristics and microstructure evolution in grey cast iron were investigated through Jmat-Pro simulations and quenching performed during directional solidification. The phase transition sequence of grey cast iron was determined as L → L + γ→ L + γ + G →γ + G → P(α + Fe_3C) + α + G. The graphite can be formed in three ways: directly nucleated from liquid through the eutectic reaction(L →γ + G), independently precipitated from the oversaturated γ phase(γ→γ + G), and produced via the eutectoid transformation(γ→ G + α). The area fraction and length of graphite as well as the primary dendrite spacing decrease with increasing cooling rate. Type-A graphite is formed at a low cooling rate, whereas a high cooling rate results in the precipitation of type-D graphite. After analyzing the graphite precipitation in the as-cast and transition regions separately solidified with and without inoculation, we concluded that, induced by the inoculant addition, the location of graphite precipitation changes from mainly the γ interdendritic region to the entire γ matrix. It suggests that inoculation mainly acts on graphite precipitation in the γ matrix, not in the liquid or at the solid–liquid front.

关键词： directional solidification grey cast iron phase transition graphite

Evolution of the microstructure and solute distribution of Sn-10wt% Bi alloys during electromagnetic field-assisted directional solidification

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Journal of Materials Science & Technology 2019年第4期35卷 568-577页

作者： Zhe Shen Minghu Peng Dongsheng Zhu Tianxiang Zheng Yunbo Zhong Weili Ren Chuanjun Li Weidong Xuan Zhongming Ren State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering Shanghai University

The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magnetic field(TSMF) and an external direct current(DC) have been investigated experimentally and numerically. The experimental results show that the solid-liquid interface will gradually become sloping with the increase of the forced flow velocity when the thermoelectric magnetic convection(TEMC)dominates the forced flow at solidification front. However, the interface will gradually become planar as the flow velocity further increases when the electromagnetic convection(EMC) dominates the forced flow. Moreover, when the flow velocity gradually increases, the primary dendrite spacing decreases from384 to 105 μm accordingly. The simulation results show that the solute distribution at the two sides of the sample can be significantly changed by the forced flow at solidification front. The rejected solute will be unidirectionally transported to one side of the sample along the TEMC(a low-velocity forced flow),thereby causing the formation of a sloping interface. However, the rejected solute will be returned back along the EMC(a higher-velocity force flow), which results in a planar interface. Furthermore, the solute content at the two sides of the sample under the forced flows at different velocities was measured. The results are in good agreement with the simulation results, which shows that the solute content difference between the two sides of the sample reaches the maximum when a 0.5 T TSMF is applied, while the solute content difference decreases to zero with a simultaneous application of a 0.5 T TSMF and a 1.6 × 10~5 A/m^2 external DC.

关键词： directional solidification Sn-Bi alloy Forced flow Solute distribution Numerical simulation Electromagnetic field

Structural basis for directional chitin biosynthesis

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四川生理科学杂志 2022年第9期44卷 1621-1621页

作者： Wei Chen State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection Chinese Academy of Agricultural Sciences Beijing China Shenzhen Branch Guangdong Laboratory of Lingnan Modern Agriculture Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs Agricultural Genomics Institute at Shenzhen Chinese Academy of Agricultural Sciences Shenzhen China School of Bioengineering Dalian University of Technology Dalian China Faculty of Environment and Life Beijing University of Technology Beijing China Tianjin Key Laboratory for Modern Drug Delivery and High-Efficiency Collaborative Innovation Center of Chemical Science and Engineering School of Pharmaceutical Science and Technology Tianjin University Tianjin China Center for Multi-disciplinary Research Institute of High Energy Physics Chinese Academy of Sciences Beijing China Department of Chemistry and Biology School of Science and Technology University of Siegen Siegen Germany

Chitin,the most abundant aminopolysaccharide in nature,is an extracellular polymer consisting of N-acetylglucosamine(GlcNAc)units1.The key reactions of chitin biosynthesis are catalysed by chitin synthase2-4,a membrane-integrated glycosyltransferase that transfers GlcNAc from UDP-GlcNAc to a growing chitin chain.However,the precise mechanism of this process has yet to be elucidated.Here we report five cryo-electron microscopy structures of a chitin synthase from the devastating soybean root rot pathogenic oomycete Phytophthora sojae(PsChs1).They represent the apo,GlcNAc-bound,nascent chitin oligomer-bound,UDP-bound(post-synthesis)and chitin synthase inhibitor nikkomycin Z-bound states of the enzyme,providing detailed views into the multiple steps of chitin biosynthesis and its competitive inhibition.The structures reveal the chitin synthesis reaction chamber that has the substrate-binding site,the catalytic centre and the entrance to the polymer-translocating channel that allows the product polymer to be discharged.This arrangement reflects consecutive key events in chitin biosynthesis from UDP-GlcNAc binding and polymer elongation to the release of the product.We identified a swinging loop within the chitin-translocating channel,which acts as a'gate lock'that prevents the substrate from leaving while directing the product polymer into the translocating channel for discharge to the extracellular side of the cell membrane.This work reveals the directional multistep mechanism of chitin biosynthesis and provides a structural basis for inhibition of chitin synthesis.

关键词： directional locating arrangement

Heat Transfer Analysis During "One-Step" directional Solidification Process for Giant Magnetostrictive Materials

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Journal of Rare Earths 2004年第Z2期22卷 183-185页

作者： Li Kuoshe Yang Hongchuan Xu Jing Yuan Yongqiang Yu Dunbo Li Hongwei Grirem Advanced Materials Co. LtdGeneral Research Institute for Nonferrous MetalsBeijing 100088China Grirem Advanced Materials Co.LtdGeneral Research Institute for Nonferrous MetalsBeijing 100088China Grirem Advanced Materials Co.LtdGeneral Research Institute for Nonferrous MetalsBeijing 100088China Grirem Advanced Materials Co.LtdGeneral Research Institute for Nonferrous MetalsBeijing 100088China Grirem Advanced Materials Co.LtdGeneral Research Institute for Nonferrous MetalsBeijing 100088China Grirem Advanced Materials Co.LtdGeneral Research Institute for Nonferrous MetalsBeijing 100088China

By theoretical analysis of heat transfer during the "one-step" directional solidification process, the functional relation between the temperature in solid-liquid interface and its effect factor was studied. The thermal gradient in solid liquid interface and heat transfer coefficient between the samples and surroundings were also calculated. On the basis of the above analysis, some suggestions for improving the thermal gradient in solid-liquid interface were put forward. It will provide a theoretical instruction for preparing high performance giant magnetostrictive materials (GMM).

关键词： directional solidification "one-step" process heat transfer solid-liquid interface thermal gradient