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ARAP++:an extension of the local/global approach to mesh parameterization

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Frontiers of Information Technology & Electronic Engineering 2016年第6期17卷 501-515页

作者： Zhao WANG Zhong-xuan LUO jie-lin zhang Emil SAUCAN School of Mathematical Sciences Dalian University of TechnologyDalian 116024China School of Software Dalian University of TechnologyDalian 116620China Max Planck Institute for Mathematics in the Sciences Leipzig 70569Germany

Mesh parameterization is one of the fundamental operations in computer graphics(CG) and computeraided design(CAD). In this paper, we propose a novel local/global parameterization approach, ARAP++, for singleand multi-boundary triangular meshes. It is an extension of the as-rigid-as-possible(ARAP) approach, which stitches together 1-ring patches instead of individual triangles. To optimize the spring energy, we introduce a linear iterative scheme which employs convex combination weights and a fitting Jacobian matrix corresponding to a prescribed family of transformations. Our algorithm is simple, efficient, and robust. The geometric properties(angle and area)of the original model can also be preserved by appropriately prescribing the singular values of the fitting matrix. To reduce the area and stretch distortions for high-curvature models, a stretch operator is introduced. Numerical results demonstrate that ARAP++ outperforms several state-of-the-art methods in terms of controlling the distortions of angle, area, and stretch. Furthermore, it achieves a better visualization performance for several applications, such as texture mapping and surface remeshing.

关键词： Mesh parameterization Convex combination weights Stretch operator Jacobian matrix

Improving thermal efficiency and stability of laser welding process for magnesium alloy by combining power modulation and subatmospheric pressure environment

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Journal of Magnesium and Alloys 2022年第10期10卷 2788-2800页

作者： jie Ning Suck-Joo Na lin-jie zhang Xiang Wang Jian Long Won-Ik Cho State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China BIAS-Bremer Institut für angewandte Strahltechnik GmbH Klagenfurter Straße 528359 BremenGermany

The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor *** solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were *** AZ31magnesium(Mg)alloy was used as the test *** test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal *** the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole ***,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably *** LW in subatmospheric environment,the weld penetration can be further greatly increased through power ***,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded ***,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was *** was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

关键词： Laser welding Subatmospheric environment Power modulation Highly reflective materials Thermal efficiency Stability

Improvement in the weldability of molybdenum alloy by pre-welding solid carburising

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Journal of Materials Science & Technology 2021年第21期80卷 1-12页

作者： Liang-Liang zhang lin-jie zhang Jian Long Xiang-Dong Ding Jun Sun Yuan-Jun Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China

Molybdenum(Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry;however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone(FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo_(2)C, and some free C atoms, and MoC and MoOxC yphases were also present. The distribution of Mo_(2)C directly influenced the bonding strength of the grain *** Mo_(2)C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo,it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo_(2)C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoOxC yphase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.

关键词： Molybdenum Carbon Mo_(2)C Laser beam welding Pre-welding solid carburising

Toughening additive manufactured Zr-based bulk metallic glass composites by martensite phase transformation

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Journal of Materials Science & Technology 2024年第3期170卷 95-102页

作者： Pengcheng zhang Cheng zhang jie Pan Di Ouyang lin Liu State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Additive manufacturing technology based on laser powder bed fusion(LPBF)offers a novel approach for fabricating bulk metallic glass(BMG)products without restriction in size and ***,the BMGs prepared by LPBF usually suffered from less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones(HAZs).Since crystallization in HAZs is hard to avoid completely in LPBF BMGs,it is desirable to design a suitable alloy system,in which only ductile crystalline phase,instead of brittle intermetallics,is formed in *** unique structure could effectively increase the toughness/plasticity of the LPBF *** achieve this goal,a quaternary BMG system with a composition of Zr_(47.5)Cu_(45.5)Al_(5)Co_(2)is adopted and subjected to *** is found that nearly a single phase of B_(2)-ZrCu is precipitated in HAZs,while a fully amorphous phase is formed in molten pools(MPs).This B_(2)phase reinforced BMG composite exhibits excellent mechanical properties with enhanced plasticity and ***,it is easy to modulate the mechanical properties by altering the amount of the B_(2)phase via adjusting the laser energy ***,the best combination of strength,plasticity,and notch toughness is obtained in the BMG composite containing 27.4%B_(2)phase and 72.6%amorphous phase,which exhibits yield strength(σ_(s))of 1423 MPa,plastic strain(ε_(p))of 4.65%,and notch toughness(K_(q))of 53.9 MPa m 1/***,a notable strain-hardening is also *** improvement of plasticity/toughness and appearance of strain-hardening behavior are mainly due to the martensite phase transformation from the B_(2)phase to the Cm phase during plastic deformation(i.e.,the phase transformation-induced plasticity effect).The current work provides a guide for making advanced BMGs and BMG composites by additive manufacturing.

关键词： Laser powder bed fusion Bulk metallic glass composites Phase transformation-induced plasticity Deformation mechanism

Effect of Ti-Hf-Zr-Cu-Ni high entropy alloy addition on laser beam welded joint of Ti2AlNb based intermetallic alloy

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Journal of Materials Science & Technology 2022年第25期120卷 214-226页

作者： Mirza Zahid Hussain Jiangtao Xiong Jinglong Li Farah Siddique lin jie zhang Yajie Du Xian Rong Zhou State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710072China

TiAlNb based intermetallic alloys,a potential competitor for next-generation super alloys,are susceptible to high-temperature embrittlement due to nucleation of a metastable single B2 phase in the fusion zone(FZ)during laser beam welding(LBW).In this study,a high entropy alloy(HEA),Ti-Hf-Zr-Cu-Ni,was self-developed and introduced as an interlayer into laser beam welded joint(LBWJ)of Ti-22 Al-27 Nb to analyze its impact on the evolution of microstructure in the weld zone(WZ)and subsequently on joint *** examination was carried out through electron probe micro analysis(EPMA),electron backscattered diffraction(EBSD)analysis,high-resolution scanning transmission electron microscopy(HRSTEM)comprising bright field(BF),selective area electron diffraction(SAED)and high angle annular dark-field(HAADF)*** of the HEA into FZ of LBWJ triggered heterogenous nucleation during solidification,resultantly,fine-grained B2 with a greater proportion of high angle grain boundaries(HAGBs)was *** of Ti-22 Al-27 Nb LBWJ,prepared with an interlayer of HEA,was composed of planar,cellular,columnar and equiaxed dendritic grains;a solidification mode which was different from that observed in LBWJ prepared without adulteration of the *** impact of heterogenous nucleation during epitaxial solidification on mechanical properties was established through micro vickers hardness mapping and tensile test,conducted at room *** average hardness,343.5 HV,in the FZ of LBWJ prepared with an interlayer of HEA,was compatible with that of base material(BM),345 *** ultimate tensile strength(UTS),1062 MPa,and percentage elongation,11.2%,of the HEA tempered LBWJ were found in close approximation with that of BM,1060 MPa and 13.4%,respectively.A ductile mode of failure was observed during tensile test of the Ti-Hf-Zr-Cu-Ni supplemented LBWJ of Ti-22 Al-27 Nb,while quasi-cleavage mode of fracture was apparent in the joint of Ti-22 Al-27 Nb welded with

关键词： Laser beam welding Ti2Al Nb based intermetallics High entropy alloy Heterogenous nucleation

Non-crossover sub-Doppler DAVLL in selective reflection scheme

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Chinese Physics B 2019年第8期28卷 190-194页

作者： lin-jie zhang Hao zhang Yan-Ting Zhao Lian-Tuan Xiao Suo-Tang Jia State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Laser SpectroscopyShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

We demonstrate a non-crossover sub-Doppler dichroic atomic vapor laser locking(DAVLL)in selective reflection scheme,which allows us to obtain a modulation-free laser locking with wide tuneable *** dependence of peak-to-peak amplitude,tuneable range and the slope near the zero-crossing point of error signal on the frequency shift induced by the magnetic fields are *** adjustable error signal by the varying external magnetic field can offer the laser locking from the order of tens MHz to hundreds *** ultimate dither of locked laser frequency is less than 0.5 *** square root of Allan variance of the error signals reaches a minimum of 3×10^-10 for an averaging time of 130 s.

关键词： reflection spectrum DAVLL sub-Doppler frequency stabilization

Process intensification for the synthesis and purification of battery-grade Li_(2)CO_(3)with microfluidics

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Particuology 2024年第7期90卷 106-117页

作者： Haodu Li jie zhang lin Dai Le Du Jiqin Zhu The State Key Laboratory of Chemical Resource Engineering College of Chemical EngineeringBeijing University of Chemical TechnologyBeijing 100029China

Battery-grade lithium carbonate(Li_(2)CO_(3))with a purity of higher than 99.5 wt%is of great importance as a high value-added lithium ***,influences of different reaction systems and process control on product purity remain ***,a membrane dispersion microreactor was used to enhance the mass transfer of preparation and purification processes in homogeneous and heterogeneous *** systems of Na_(2)CO_(3)–LiCl,NH_(4)HCO_(3)–LiCl,and NH_(3)·H_(2)O−CO_(2)−LiCl,CO_(2)purification based on carbonation and decomposition were *** Li_(2)CO_(3)purity was increased by the improvement of mixing *** carbonation time was reduced by 62.5%and 58.3%for the NH_(3)·H_(2)O−CO_(2)and CO_(2)purification systems,*** the two ammonia-based systems,Li_(2)CO_(3)particles with a purity of 99.7–99.8 wt%were one-step prepared with a size of 3–5μm,which also met the requirement of the battery-grade *** purity was further increased to 99.9 wt%by CO_(2)purification and LiHCO_(3)*** investigation could provide a feasible alternative for the controllable preparation of battery-grade Li_(2)CO_(3)in one or multiple steps.

关键词： Microfluidics Battery grade Li_(2)CO_(3) Process intensification High purity

Predicting Acute Mountain Sickness Using Regional Sea-Level Cerebral Blood Flow

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Biomedical and Environmental Sciences 2024年第8期37卷 887-896页

作者： Hao zhang jie Feng Shiyu zhang Wenjia Liu lin Ma Chinese PLA Medical School Beijing 100853China Department of Radiology First Medical CenterChinese PLA General HospitalBeijing 100853China Department of Radiology Beijing Friendship HospitalCapital Medical UniversityBeijing 100050China

Objective To investigate the role of sea-level cerebral blood flow(CBF)in predicting acute mountain sickness(AMS)using three-dimensional pseudo-continuous arterial spin labeling(3D-pCASL).Methods Forty-eight healthy volunteers reached an altitude of 3,650 m by air after undergoing a head magnetic resonance imaging(MRI)including 3D-pCASL at sea *** CBF values of the bilateral anterior cerebral artery(ACA),middle cerebral artery(MCA),posterior cerebral artery(PCA),and posterior inferior cerebellar artery(PICA)territories and the laterality index(LI)of CBF were compared between the AMS and non-AMS *** analyses were performed to determine the relationship between CBF and AMS,and the predictive performance was assessed using receiver operating characteristic(ROC)*** The mean cortical CBF in women(81.65±2.69 mL/100 g/min)was higher than that in men(74.35±2.12 mL/100 g/min)(P<0.05).In men,the cortical CBF values in the bilateral ACA,PCA,PICA,and right MCA were higher in patients with AMS than in those *** CBF in the right PCA best predicted AMS(AUC=0.818).In women,the LI of CBF in the ACA was different between the AMS and non-AMS groups and predicted AMS with an AUC of *** Although the mechanism and prediction of AMS are quite complicated,higher cortical CBF at sea level,especially the CBF of the posterior circulatory system,may be used for prediction in male volunteers using non-invasive 3D-pCASL.

关键词： Acute mountain sickness High-altitude headache Cerebral blood flow Arterial spin labeling Magnetic resonance imaging

Research on intelligent search-and-secure technology in accelerator hazardous areas based on machine vision

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Nuclear Science and Techniques 2024年第4期35卷 96-107页

作者： Ying-lin Ma Yao Wang Hong-Mei Shi Hui-jie zhang School of Traffic and Transportation Beijing Jiaotong UniversityBeijing 100044China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China

Prompt radiation emitted during accelerator operation poses a significant health risk,necessitating a thorough search and securing of hazardous areas prior to ***,manual sweep methods are ***,the limitations of manual sweeps have become increasingly evident with the implementation of large-scale *** leveraging advancements in machine vision technology,the automatic identification of stranded personnel in controlled areas through camera imagery presents a viable solution for efficient search and *** the criticality of personal safety for stranded individuals,search and security processes must be sufficiently *** ensure comprehensive coverage,180°camera groups were strategically positioned on both sides of the accelerator tunnel to eliminate blind spots within the monitoring *** YOLOV8 network model was modified to enable the detection of small targets,such as hands and feet,as well as larger targets formed by individuals near the ***,the system incorporates a pedestrian recognition model that detects human body parts,and an information fusion strategy is used to integrate the detected head,hands,and feet with the identified pedestrians as a cohesive *** strategy enhanced the capability of the model to identify pedestrians obstructed by equipment,resulting in a notable improvement in the recall ***,recall rates of 0.915 and 0.82were obtained for Datasets 1 and 2,*** there was a slight decrease in accuracy,it aligned with the intended purpose of the search-and-secure software *** tests conducted within an accelerator tunnel demonstrated the effectiveness of this approach in achieving reliable recognition outcomes.

关键词： Search and secure Machine vision Camera Human body parts recognition Particle accelerator Hazardous area