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Effects of nozzle and fluid properties on the drop formation dynamics in a drop-on-demand inkjet printing

applied Mathematics and mechanics(English Edition) 2019年第9期40卷 1239-1254页

作者： A. B. AQEEL M. MOHASAN Pengyu LV Yantao YANG Huiling DUAN State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science Beijing Innovation Center for Engineering Science and Advanced Technology College of Engineering Peking University Beijing 100871 China National University of Sciences and Technology H-12 Islamabad Pakistan Center for Applied Physics and Technology Key Laboratory of High Energy Density Physics and Inertial Fusion Sciences and Application Collaborative Innovation Center of Ministry of Education Peking University Beijing 100871 China

The droplet formation dynamics of a Newtonian liquid in a drop-on-demand (DOD) inkjet process is numerically investigated by using a volume-of-fluid (VOF) method. We focus on the nozzle geometry, wettability of the interior surface, and the fluid properties to achieve the stable droplet formation with higher velocity. It is found that a nozzle with contracting angle of 45° generates the most stable and fastest single droplet, which is beneficial for the enhanced printing quality and high-throughput printing rate. For this nozzle with the optimal geometry, we systematically change the wettability of the interior surface, i.e., different contact angles. As the contact angle increases, pinch-off time increases and the droplet speed reduces. Finally, fluids with different properties are investigated to identify the printability range.

关键词： inkjet printing drop-on-demand (DOD) droplet formation nozzle geometry surface wettability printability range

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Mechanical activation of spike fosters SARS-CoV-2 viral infection

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细胞研究（英文版） 2021年第10期31卷 1047-1060页

作者： Wei Hu Yong Zhang Panyu Fei Tongtong Zhang Danmei Yao Yufei Gao Jia Liu Hui Chen Qiao Lu Tenny Mudianto Xinrui Zhang Chuxuan Xiao Yang Ye Qiming Sun ling Zhang Qi Xie Pei-Hui Wang Jun Wang Zhenhai Li Jizhong Lou Wei Chen Department of Cardiology of the Second Affiliated Hospital and Department of Cell Biology Zhejiang University School of MedicineHangzhouZhejiangChina Key Laboratory of RNA Biology CAS Center for Excellence in BiomacromoleculesInstitute of BiophysicsChinese Academy of SciencesBeijingChina Department of Cardiology of the Second Affiliated Hospital and Department of Cell Biology Zhejiang University School of MedicineHangzhouZhejiangChina School of Mechanical Engineering Zhejiang UniversityHangzhouZhejiangChina Department of Cardiology of the Second Affiliated Hospital and Department of Cell Biology Zhejiang University School of MedicineHangzhouZhejiangChina Department of Hepatobiliary and Pancreatic Surgery The Center for Integrated Oncology and Precision MedicineAffiliated Hangzhou First People's HospitalZhejiang University School of MedicineHangzhouZhejiangChina Department of Pathology New York University Grossman School of MedicineNew YorkNYUSA The Laura and Isaac Perlmutter Cancer Center New York University Langone HealthNew YorkNYUSA Department of Pathology New York University Grossman School of MedicineNew YorkNYUSA Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases the MOE Frontier Science Center for Brain Science & Brain-machine IntegrationState Key Laboratory for Modern Optical Instrumentation Key Laboratory for Biomedical Engineering of the Ministry of EducationCollege of Biomedical Engineering and Instrument ScienceZhejiang UniversityHangzhouZhejiangChina Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijingChina Advanced Medical Research Institute Cheeloo College of MedicineShandong UniversityJinanShandongChina Westlake Institute for Advanced Study School of Life SciencesWestlake UniversityHangzhouZhejiangChina Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceSh

The outbreak of SARS-CoV-2 (SARS2) has caused a global COVID-19 *** spike protein of SARS2 (SARS2-S) recognizes host receptors,including ACE2,to initiate viral entry in a complex biomechanical ***,we reveal that tensile force,generated by bending of the host cell membrane,strengthens spike recognition of ACE2 and accelerates the detachment of spike's S1 subunit from the S2 subunit to rapidly prime the viral fusion ***,such mechano-activation is fulfilled by force-induced opening and rotation of spike's receptor-binding domain to prolong the bond lifetime of spike/ACE2 binding,up to 4 times longer than that of SARS-S binding with ACE2 under 10 pN force application,and subsequently by force-accelerated S1/S2 detachment which is up to ～103 times faster than that in the no-force ***,the SARS2-S D614G mutant,a more infectious variant,shows 3-time stronger force-dependent ACE2 binding and 35-time faster force-induced S1/S2 *** also reveal that an anti-S1/S2 non-RBD-blocking antibody that was derived from convalescent COVlD-19 patients with potent neutralizing capability can reduce S1/S2 detachment by 3 × 106 times under *** study sheds light on the mechano-chemistry of spike activation and on developing a non-RBD-blocking but S1/S2-locking therapeutic strategy to prevent SARS2 invasion.

关键词： Molecular biology Structural biology

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Teaching mechanics with individual exercise assignments and automated correction

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PAMM 2023年第3期23卷

作者： Michael H. Gfrerer Benjamin Marussig Katharina Maitz Mia M. Bangerl Institute of Applied Mechanics Graz Center of Computational Engineering (GCCE) Graz University of Technology Graz Austria Private University College of Teacher Education Augustinum (PPH Augustinum) Graz Austria Institute of Interactive Systems and Data Science Graz University of Technology Graz Austria

Solving exercise problems by yourself is a vital part of developing a mechanical understanding. Yet, most mechanics lectures have more than 200 participants, so the workload for manually creating and correcting assignments limits the number of exercises. The resulting example pool is usually much smaller than the number of participants, making verifying whether students can solve problems themselves considerably harder. At the same time, unreflected copying of tasks already solved does not foster the understanding of the subject and leads to a false self-assessment. We address these issues by providing a scalable approach for creating, distributing, and correcting exercise assignments for problems related to statics, strength of materials, dynamics, and hydrostatics. The overall concept allows us to provide individual exercise assignments for each student. A quantitative survey among students of our recent statics lecture assesses the acceptance of our teaching tool. The feedback indicates a clear added value for the lecture, which fosters self-directed and reflective learning.

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Correction to: Influence of sustained mild dehydration on thermoregulatory and cognitive functions during prolonged moderate exercise

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European journal of applied physiology 2024年第12期124卷 2024 Oct 9页

作者： Hironori Watanabe Yuma Kadokura Taisuke Sugi Kiyoshi Saito Kei Nagashima Institute for Energy and Environmental System Sustainable Energy & Environmental Society Open Innovation Research Organization Waseda University 3-4-1 Okubo Shinjuku-ku Tokyo 1698555 Japan. Advanced Research Center for Human Sciences Waseda University 2-579-15 Mikajima Tokorozawa Saitama 3591192 Japan. Body Temperature and Fluid Laboratory Faculty of Human Sciences Waseda University 2-579-15 Mikajima Tokorozawa Saitama 3591192 Japan. Infrastructure Systems Research & Development Center Toshiba Infrastructure Systems & Solutions Corporation Kawasaki Kanagawa 2129595 Japan. Department of Applied Mechanics and Aerospace Engineering School of Fundamental Science and Engineering Waseda University 3-4-1 Okubo Shinjuku-ku Tokyo 1698555 Japan. Institute for Energy and Environmental System Sustainable Energy & Environmental Society Open Innovation Research Organization Waseda University 3-4-1 Okubo Shinjuku-ku Tokyo 1698555 Japan. k-nagashima@waseda.jp. Body Temperature and Fluid Laboratory Faculty of Human Sciences Waseda University 2-579-15 Mikajima Tokorozawa Saitama 3591192 Japan. k-nagashima@waseda.jp.

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Subwavelength Photorefractive Grating in a Thin-Film Lithium Niobate Microcavity

arXiv

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arXiv 2024年

作者： Hou, Jiankun Zhu, Jiefu Ma, Ruixin Xue, Boyi Zhu, Yicheng Lin, Jintian Jiang, Xiaoshun Chen, Xianfeng Cheng, Ya Ge, Li Zheng, Yuanlin Wan, Wenjie State Key Laboratory of Advanced Optical Communication Systems and Networks University of Michigan Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong University Shanghai200240 China School of Physics and Astronomy Shanghai Jiao Tong University Shanghai200240 China State Key Laboratory of High Field Laser Physics CAS Center for Excellence in Ultra-Intense Laser Science Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai201800 China National Laboratory of Solid-State Microstructures College of Engineering and Applied Science School of Physics Nanjing University Nanjing210093 China Department of Physics and Astronomy College of Staten Island The City University of New York NY10314 United States

Subwavelength gratings play a fundamental and pivotal role in numerous science and applications for wave manipulation, exhibiting distinctive features such as filtering, phase manipulation, and anti-reflection. However, conventional fabrication methods for ultrasmall periodic structures are constrained by the fundamental optical diffraction limit, making it challenging to produce subwavelength gratings for optics. Here, we demonstrate a novel technique to build a reconfigurable subwavelength photorefractive grating (SPG) in a thin-film lithium niobate on the platform of an optical microcavity. Such SPGs are optically induced through the photorefractive effect and the subwavelength features originate from the spatial phase modulations of the pump’s standing wave. The resulting SPGs lead to the mode splitting of two counter-propagating modes inside the microcavity, exhibiting an Electromagnetically Induced Transparency (EIT)-like transmission spectrum. Moreover, the unique subwavelength characteristic of SPGs enables first-order quasi-phase-matching for backward second-harmonic generation, a longstanding problem in nonlinear optics. Also, free-space-to-chip vertical nonlinear frequency conversion can be achieved in a similar manner. These results provide a flexible approach towards fabricating subwavelength gratings, which holds significant potential in various applications such as nonlinear frequency conversion, optical communication, sensing, and quantum technologies. © 2024, CC BY.

关键词： Microcavities

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Enhanced Frequency Conversion in Parity-Time Symmetry Line

arXiv

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arXiv 2024年

作者： Hou, Jiankun Zhu, Jiefu Ma, Ruixin Xue, Boyi Zhu, Yicheng Lin, Jintian Jiang, Xiaoshun Zheng, Yuanlin Chen, Xianfeng Cheng, Ya Ge, Li Wan, Wenjie State Key Laboratory of Advanced Optical Communication Systems and Networks University of Michigan-Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong University Shanghai200240 China Department of Physics and Astronomy Shanghai Jiao Tong University Shanghai200240 China State Key Laboratory of High Field Laser Physics CAS Center for Excellence in Ultra-Intense Laser Science Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai201800 China National Laboratory of Solid-State Microstructures College of Engineering and Applied Science School of Physics Nanjing University Nanjing210093 China Department of Physics and Astronomy College of Staten Island the City University of New York NY10314 United States

Non-Hermitian degeneracies reveal intriguing and non-trivial behaviors in open physical systems. Examples like Parity-Time (PT) symmetry breaking, topological encircling chirality, and enhanced sensing near an exceptional point (EP) are often associated with the abrupt nature of the phase transition around these degeneracies. Here we experimentally observe a cavity-enhanced second-harmonic frequency (SHG) conversion on a PT symmetry line, i.e. a set consisting of open-ended isofrequency or isoloss lines, both terminated at EPs on the Riemann surface in parameter space. The enhancement factor can reach as high as 300, depending on the crossing point whether in the symmetry or the broken phase of the PT line. Moreover, such enhancement of SHG enables sensitive distance sensing with a nanometer resolution. Our works may pave the way for practical applications in sensing, frequency conversion, and coherent wave control. © 2024, CC BY.

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First-principles calculation of electroacoustic properties of wurtzite (Al,Sc)N

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Physical Review B 2021年第11期103卷 115204-115204页

作者： Daniel F. Urban Oliver Ambacher Christian Elsässer Fraunhofer Institute for Mechanics of Materials IWM Wöhlerstrasse 11 79108 Freiburg Germany Fraunhofer Institute for Applied Solid State Physics IAF Tullastrasse 72 79108 Freiburg Germany INATECH–Department of Sustainable Systems Engineering Albert-Ludwigs-Universität Freiburg Emmy-Noether-Strasse 2 79110 Freiburg Germany Freiburg Materials Research Center (FMF) Albert-Ludwigs-Universität Freiburg Stefan-Meier-Strasse 21 79104 Freiburg Germany

We study the electroacoustic properties of aluminum scandium nitride crystals Al1−xScxN with the metastable wurtzite structure by means of first-principles calculations based on density functional theory. We extract the material property data relevant for electroacoustic device design, namely, the full tensors of elastic and piezoelectric constants. Atomistic models were constructed and analyzed for a variety of Sc concentrations 0≤x≤50%. The functional dependence of the material properties on the scandium concentration was extracted by fitting the data obtained from an averaging procedure for different disordered atomic configurations. We give an explanation of the observed elastic softening and the extraordinary increase in piezoelectric response as a function of Sc content in terms of an element-specific analysis of bond lengths and bond angles.

关键词： Elasticity First-principles calculations Piezoelectricity Disordered alloys Piezoelectrics Wurtzite Density functional calculations

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DeepFlame: A deep learning empowered open-source platform for reacting flow simulations

arXiv

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arXiv 2022年

作者： Mao, Runze Lin, Minqi Zhang, Yan Zhang, Tianhan John Xu, Zhi-Qin Chen, Zhi X. State Key Laboratory of Turbulence and Complex Systems Aeronautics and Astronautics College of Engineering Peking University Beijing100871 China Ai for Science Institute Beijing100080 China Caep Software Center for High Performance Numerical Simulation Beijing100088 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Department of Mechanics and Aerospace Engineering SUSTech Shenzhen518055 China Institute of Natural Sciences School of Mathematical Sciences Shanghai Jiao Tong University Shanghai200240 China MOE-LSC Qing Yuan Research Institute Shanghai Jiao Tong University Shanghai200240 China

Recent developments in deep learning have brought many inspirations for the scientific computing community and it is perceived as a promising method in accelerating the computationally demanding reacting flow simulations. In this work, we introduce DeepFlame, an open-source C++ platform with the capabilities of utilising machine learning algorithms and pre-trained models to solve for reactive flows. We combine the individual strengths of the computational fluid dynamics library OpenFOAM, machine learning framework Torch, and chemical kinetics program Cantera. The complexity of cross-library function and data interfacing (the core of DeepFlame) is minimised to achieve a simple and clear workflow for code maintenance, extension and upgrading. As a demonstration, we apply our recent work on deep learning for predicting chemical kinetics (Zhang et al. Combust. Flame vol. 245 pp. 112319, 2022) to highlight the potential of machine learning in accelerating reacting flow simulation. A thorough code validation is conducted via a broad range of canonical cases to assess its accuracy and efficiency. The results demonstrate that the convection-diffusion-reaction algorithms implemented in DeepFlame are robust and accurate for both steady-state and transient processes. In addition, a number of methods aiming to further improve the computational efficiency, e.g. dynamic load balancing and adaptive mesh refinement, are explored. Their performances are also evaluated and reported. With the deep learning method implemented in this work, a speed-up of two orders of magnitude is achieved in a simple hydrogen ignition case when performed on a medium-end graphics processing unit (GPU). Further gain in computational efficiency is expected for hydrocarbon and other complex fuels. A similar level of acceleration is obtained on an AI-specific chip - deep computing unit (DCU), highlighting the potential of DeepFlame in leveraging the next-generation computing architecture and hardware. © 202

关键词： Graphics processing unit

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Coupling effect of wall slip and spanwise oscillation on drag reduction in turbulent channel flow

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Physical Review Fluids 2020年第12期5卷 124601-124601页

作者： Zexiang Li Songsong Ji Huiling Duan Shilong Lan Jinbai Zhang Pengyu Lv State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science BIC-ESAT College of Engineering Peking University Beijing 100871 China Key Laboratory of High Energy Density Physics Simulation Center for Applied Physics and Technology Peking University Beijing 100871 China National Laboratory of Computational Fluid Dynamics Beihang University Beijing 100191 China

The coupling effect of the isotropic wall slip and the spanwise oscillation boundary conditions on the drag reduction and turbulence properties are studied by direct numerical simulations. As the slip length increases, the drag reduction gradually changes from the oscillation dominated to the slip dominated. The increase of slip length will decrease the maximum spanwise velocity of the fluid on the wall, which is responsible for the decreased ability of the oscillatory wall motion to reduce the skin-friction drag. The drag reduction decomposition shows that the contribution from the modifications of turbulent dynamics will undergo a shift from drag increase to drag reduction as the isotropic slip length increases. Compared with the respective no-slip reference flow, the drag reduction of wall slip in laminar and turbulent channel flows can be expressed in a unified form versus the outer scale slip length. Furthermore, many aspects of the turbulence properties are influenced by the coupling effect. First, the wall slip condenses the envelope range of the phase fluctuations caused by the oscillatory wall motion, as well as the magnitude of the periodic fluctuation of the phase-averaged friction coefficient. Second, an unexpected property of the coupled boundary condition is found that the existence of the Stoke layer delays the relaminarization process caused by the large slip length. Third, the wall slip would narrow the periodic inclination of the streaks and then inhibit the energy transfer process in the horizontal direction. Fourth, in terms of phase, the Stokes strain and the shear angle have the same lag phase with the spanwise velocity, while the hysteresis of turbulent dynamics leads to the larger lag phase of the streaks and phase-averaged friction coefficient. These new features are valuable for increasing knowledge on this topic.

关键词： Slip boundary effects Turbulence Wall slip

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Configurable Phase Transitions in a Topological Thermal Material

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Physical Review Letters 2021年第10期127卷 105901-105901页

作者： Guoqiang Xu Ying Li Wei Li Shanhui Fan Cheng-Wei Qiu Department of Electrical and Computer Engineering National University of Singapore Kent Ridge 117583 Republic of Singapore Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou 310027 China International Joint Innovation Center Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang The Electromagnetics Academy at Zhejiang University Zhejiang University Haining 314400 China GPL Photonics Laboratory State Key Laboratory of Applied Optics Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130033 China Department of Electrical Engineering and Ginzton Laboratory Stanford University Stanford California 94305 USA

Diffusive nature of thermal transportation fundamentally restricts topological characteristics due to the absence of a sufficient parametric space with complex dimensionalities. Here, we create an orthogonal advection space with two advective pairs to reveal the unexplored topological transitions in thermal material. We demonstrate four types of configurable thermal phases, including the nontrivial dynamic-equilibrium distribution, nonchiral steplike π-phase transition, and another two trivial profiles related to the anti-parity-time symmetry nature. Our findings provide a recipe for realizing a topologically robust thermal system under arbitrary perturbations.

关键词： Diffusion Heat transfer Topological insulators Topological phase transition Metamaterials Topological materials

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