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China Foundry 2024年第1期21卷 51-59页

作者： Dong Pan Qing-tao Guo Kai-lun Zhang Fu-zhi Yu Yu-ying Li Yu-bao Xiao State Key Laboratory of Metal Materials for Marine Equipment and Application Anshan 114009LiaoningChina Ansteel Beijing Research Institute Co. Ltd.Beijing 102200China

Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets.

关键词： billet electromagnetic stirring helical solidification element segregation numerical simulation

Shape Memory Alloy helical Microrobots with Transformable Capability towards Vascular Occlusion Treatment

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Research 2022年第4期2022卷 493-505页

作者： Hehua Zhang Borui Xu Yi Ouyang Yunqi Wang Hong Zhu Gaoshan Huang Jizhai Cui Yongfeng Mei Department of Materials Science Fudan UniversityShanghai 200438China Shanghai Frontiers Science Research Base of Intlligent Optoelectronics and Perception Institute of OptoelectronicsFudan UniversityShanghai 200433China Yiwu Research Institute of Fudan University Yiwu 322000ZhejiangChina International Institute for Inteligent Nanorobots and Nanosystems Fudan UniversityShanghai 200438China

Practical implementation of minimally invasive biomedical applications has been a long-sought goal for microrobots.In this field,most previous studies only demonstrate microrobots with locomotion ability or performing a single task,unable to be functionalized effectively.Here,we propose a biocompatible shape memory alloy helical microrobot with regulative structure transformation,making it possible to adjust its motion behavior and mechanical properties precisely.Especially,towards vascular occlusion problem,these microrobots reveal a fundamental solution strategy in the mechanical capability using shape memory effect.Such shape-transformable microrobots can not only manipulate thrust and torque by structure to enhance the unclogging efficiency as a microdriler but also utilize the high work energy to apply the expandable helical tail as a selfpropulsive stent.The strategy takes advantage of untethered manipulation to operate microsurgery without unnecessary damage.This study opens a route to functionalize microrobots via accurate tuning in structures,motions,and mechanical properties.

关键词： alloy shape helical

Direct observation of photonic Landau levels and helical edge states in strained honeycomb lattices

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Light(Science & Applications) 2020年第1期9卷 627-636页

作者： Omar Jamadi Elena Rozas Grazia Salerno Marijana Milicevic Tomoki Ozawa Isabelle Sagnes Aristide Lemaitre Luc Le Gratiet Abdelmounaim Harouri Iacopo Carusotto Jacqueline Bloch Alberto Amo Universite de Lille CNRSUMR 8523—PhLAM—Physique des Lasers Atomes et Molecules59000 LilleFrance Depto.de Fisica de Materiales e Instituto Nicolas Cabrera Universidad Autonoma de Madrid(UAM)28049 MadridSpain Center for Nonlinear Phenomena and Complex Systems Universite Libre de BruxellesCP 231Campus PlaineB-1050 BrusselsBelgium Universite Paris-Saclay CNRSCentre de Nanosciences et de Nanotechnologies91120 PalaiseauFrance Interdisciplinary Theoretical and Mathematical Sciences Program(iTHEMS) RIKENWakoSaitama 351-0198Japan INO-CNR BEC Center and Dipartimento di Fisica Universita di Trento38123 PovoItaly

We report the realization of a synthetic magnetic field for photons and polaritons in a honeycomb lattice of coupled semiconductor micropillars.A strong synthetic field is induced in both the s and p orbital bands by engineering a uniaxial hopping gradient in the lattice,giving rise to the formation of Landau levels at the Dirac points.We provide direct evidence of the sublattice symmetry breaking of the lowest-order Landau level wavefunction,a distinctive feature of synthetic magnetic fields.Our realization implements helical edge states in the gap between n=0 and n=±1 Landau levels,experimentally demonstrating a novel way of engineering propagating edge states in photonic lattices.In light of recent advances in the enhancement of polariton–polariton nonlinearities,the Landau levels reported here are promising for the study of the interplay between pseudomagnetism and interactions in a photonic system.

关键词： Landau helical realization

3D Janus plasmonic helical nanoapertures for polarization-encrypted data storage

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Light(Science & Applications) 2019年第1期8卷 788-796页

作者： Yang Chen Xiaodong Yang Jie Gao Department of Mechanical and Aerospace Engineering Missouri University of Science and TechnologyRollaMO 65409USA

helical structures have attracted considerable attention due to their inherent optical chirality.Here,we report a unique type of 3D Janus plasmonic helical nanoaperture with direction-controlled polarization sensitivity,which is simply fabricated via the one-step grayscale focused ion beam milling method.Circular dichroism in transmission of as large as 0.72 is experimentally realized in the forward direction due to the spin-dependent mode coupling process inside the helical nanoaperture.However,in the backward direction,the nanoaperture acquires giant linear dichroism in transmission of up to 0.87.By encoding the Janus metasurface with the two nanoaperture enantiomers having specified rotation angles,direction-controlled polarization-encrypted data storage is demonstrated for the first time,where a binary quick-response code image is displayed in the forward direction under the circularly polarized incidence of a specified handedness,while a distinct grayscale image is revealed in the backward direction under linearly polarized illumination with a specified azimuthal angle.We envision that the proposed Janus helical nanoapertures will provide an appealing platform for a variety of applications,which will range from multifunctional polarization control,enantiomer sensing,data encryption and decryption to optical information processing.

关键词： helical specified backward

helical nanostructure of tubular metal-organic complex synthesized by sonochemical process

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Science China Chemistry 2008年第10期51卷 971-975,1057-1058页

作者： WANG Ting LU XiaoMing HAN Li PANG XiaoLi YE ChaoHui Department of Chemistry Capital Normal UniversityBeijing 100037China Wuhan Institute of Physics and Mathematics Chinese Academy of SciencesWuhan 430071China

Tubular metal-organic complex (C2H9N2)2(C2H10N2)0.5[MoO2(OC6H4O)2] has been synthesized. The title complex crystallizes in the tetragonal system, space group P4(2)/n with a = 25.214(8), c = 7.484(4) ?, and Z = 8. The X-ray structural analysis of the complex reveals tube-like framework which is stabilized by hydrogen bond. Chiral anions [Mo(V)O2(OC6H4O)2]3? of the complex have two types of isomers(λ /δ configuration). helical nanostructure of this metal-organic complex was formed using a sonochemical method. Sonocation may lead to the transformation from the bulk tubular complex to the helical nanostructure. The as-synthesized nanohelices were all double-stranded and left- and right-handed nanohelices were both formed. The helical nanostructure is a new morphology of inorganic-organic hybrid materials on the nanoscale level and the exact formation mechanism of these helices still needs further investigation.

关键词： metal-organic complex helical nanostructure sonochemical method

Suppression of vortex-induced vibrations of a flexible riser by adding helical strakes

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Journal of Hydrodynamics 2019年第3期31卷 622-631页

作者： Dong-yang Chen Laith K. Abbas Guo-ping Wang Xiao-ting Rui Wei-jie Lu School of Hydraulic Energy and Power Engineering Yangzhou University Yangzhou 225127 China Institute of La unch Dynamics Nanjing University of Science and Technology Nanjing 210094 China Nanjing Aerosun Corporation Nanjing 210000 China

3-D computational fluid dynamics/ computational structure dynamics (CFD/CSD) numerical two-way coupling simulations are conducted for a flexible rise in order to study the dynamic response performance of the riser with and without helical strakes exposed to the vortex-induced vibration (VIV). The VIV responses of a PVC riser without helical strakes are computed and compared with experimental data, to verify the accuracy of the present two-way coupling method. Subsequently, the dynamic behaviors of a short PVC riser with different kinds of helical strakes are studied. The vibration amplitudes along the riser, the trajectories of the riser's monitor point and the vortex shedding contours are obtained in a series of simulations. The helical strakes5 VIV suppression mechanisms are found involving the breaking of the vortex structures and the reduction of the vortex shedding frequency of the bare riser. Moreover, a good suppression effect can be achieved by attaching the helical strake structure with a reasonable geometrical configuration (such as the appropriate strake height, strake pitch, the number of starts and strake coverages) to the flexible riser. The effect is also diverse at different reduced velocity (Ur). The remarkable effect is found at Ur = l for the short riser, with about 97% reduction in the transverse vibration response.

关键词： Vortex-induced vibration (VIV) fluid structure interaction (FSI) Two-way coupling helical strakes SST-SAS

Performance comparison of heat exchangers using sextant/trisection helical baffles and segmental ones

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Chinese Journal of Chemical Engineering 2019年第12期27卷 2892-2899页

作者： Yaping Chen Hongling Tang JiafengWu Huaduo Gu Shifan Yang Engineering Research Center of BEEE Ministry of EducationSchool of Energy and EnvironmentSoutheast UniversityNanjing 210096China Hefei Yidu Education Consulting Co.Ltd TAL Education GroupHefei 230031China

The shell side flow fields of both sextant and trisection helical baffle heat exchangers are presented on meridian and multilayer hexagon slices.It verifies that the performance of sextant schemes is better than those of the other kinds of helical baffle heat exchangers.The main mechanisms are due to the restricted leakage flow in the minimized gaps with increased baffle number and by one row of tubes dampen the leakage flow in the circumferential overlapped area of the adjacent helical baffles.The performance features were simulated on two different angled sextant helical heat exchangers and each compared with two trisection ones of either identical helical pitch or identical incline angle.The results verified that the performances of helical heat exchangers are mainly determined by the helical pitch rather than the baffle incline angle.The average values of comprehensive index hoΔpo-1/3 of the trisection helical schemes T-24.1°and T-29.7°are correspondingly 3.47%and 3.34%lower than those of the sextant ones X-20°and X-25°with identical helical pitches.The comparison results show that the average values of shell side h.***.c.hoand comprehensive index hoΔpo-1/3 of the optimal dual helix sextant scheme DX30°are respectively 7.22%and 23.56%higher than those of the segment scheme S100.

关键词： Heat transfer Computational fluid dynamics Convection helical baffle heat exchangers Sextant helical baffles

helical Wire Stress Analysis of Unbonded Flexible Riser Under Irregular Response

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Journal of Marine Science and Application 2017年第2期16卷 208-215页

作者： Kunpeng Wang Chunyan Ji School of Naval Architecture and Ocean Engineering Jiangsu University of Science and Technology Zhenjiang 212003 China

A helical wire is a critical component of an unbounded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction of the flexible riser. The present study establishes an analytical model for the axisymmetric and bending analyses of an unbonded flexible riser. The interlayer contact under axisymmetric loads in this model is modeled by setting radial dummy springs between adjacent layers. The contact pressure is constant during the bending response and applied to determine the slipping friction force per unit helical wire. The model tracks the axial stress around the angular position at each time step to calculate the axial force gradient, then compares the axial force gradient with the slipping friction force to judge the helical wire slipping region, which would be applied to determine the bending stiffness for the next time step. The proposed model is verified against the experimental data in the literature. The bending moment-curvature relationship under irregular response is also qualitatively discussed. The stress at the critical point of the helical wire is investigated based on the model by considering the local flexure. The results indicate that the present model can well simulate the bending stiffness variation during irregular response, which has significant effect on the stress of helical wire.

关键词： unbonded flexible riser interlayer interaction helical wire stress local flexure bending stiffness variation irregular response

The loss of function of HEL,which encodes a cellulose synthase interactive protein,causes helical and vine-like growth of tomato

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Horticulture Research 2020年第1期7卷 493-502页

作者： Qihong Yang Xiaoshuai Wan Jiaying Wang Yuyang Zhang Junhong Zhang Taotao Wang Changxian Yang Zhibiao Ye Key Laboratory of Horticultural Plant Biology Ministry of EducationHuazhong Agricultural UniversityWuhan 430070China

helical growth is an economical way for plant to obtain resources.The classic microtubule–microfibril alignment model of Arabidopsis helical growth involves restriction of the appropriate orientation of cellulose microfibrils appropriately in the cell walls.However,the molecular mechanism underlying tomato helical growth remains unknown.Here,we identified a spontaneous tomato helical(hel)mutant with right-handed helical cotyledons and petals but left-handed helical stems and true leaves.Genetic analysis revealed that the hel phenotype was controlled by a single recessive gene.Using map-based cloning,we cloned the HEL gene,which encodes a cellulose interacting protein homologous to CSI1 of Arabidopsis.We identified a 27 bp fragment replacement that generated a premature stop codon.Transgenic experiments showed that the helical growth phenotype could be restored by the allele of this gene from wild-type Pyriforme.In contrast,the knockout mutation of HEL in Pyriforme via CRISPR/Cas9 resulted in helical growth.These findings shed light on the molecular control of the helical growth of tomato.

关键词： helical cellulose walls

Enhanced Heat Transfer with Full Circumferential Ribs in helical Pipe

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Journal of Thermal Science 2002年第3期11卷 241-248页

作者： S.W.Chang L.M.Su T.L.Yang Department of Marine Engineering National Kaohsiung Institute of Marine Technology Kaohsiung Taiwan China Associate Professor Department of Electrical Engineering Tong Fang College of Technology and Commerce Taiwan China Associate Professor and Head of Department Department of Electrical Engineering Fortune Institute of Technology Taiwan China

This paper describes an experimental study of heat transfers in the smooth-walled and rib-roughened helical pipes with reference to the design of enhanced cooling passages in the cylinder head and liner of a marine propulsive diesel engine. The manner in which the repeated ribs modify the forced heat convection in the helical pipe is considered for the case where the flow is turbulent upon entering the coil but laminar in further downstream. A selection of experimental results illustrates the individual and interactive effects of Dean vortices and rib-flows on heat transfer along the inner and outer helixes of coils. The experimental-based observations reveal that the centrifugal force modifies the heat transfer in a manner to generate circumferential heat transfer variation with better cooling performance on the outer edge relative to its inner counterpart even with the agitated flow field caused by the repeated ribs. Heat transfer augmentation factor in the range of 1.3 ~ 3 times of the smooth-walled

关键词： helical pipe heat transfer enhancement.