Although machine Learning has demonstrated exceptional applicability in thermographic inspection,precise defect reconstruction is still challenging,especially for complex defect profiles with limited defect sample div...Although machine Learning has demonstrated exceptional applicability in thermographic inspection,precise defect reconstruction is still challenging,especially for complex defect profiles with limited defect sample diversity.Thus,this paper proposes a self-enhancement defect reconstruction technique based on cycle-consistent generative adversarial network(Cycle-GAN)that accurately characterises complex defect profiles and generates reliable artificial thermal images for dataset augmentation,enhancing defect characterisation.By using a synthetic dataset from simulation and experiments,the network overcomes the limited samples problem by learning the diversity of complex defects from finite element modelling and obtaining the thermography uncertainty patterns from practical experiments.Then,an iterative strategy with a self-enhancement capability optimises the characterisation accuracy and data generation performance.The designed loss function structure with cycle consistency and identity loss constrains the GAN’s transfer variation to guarantee augmented data quality and defect reconstruction accuracy simultaneously,while the self-enhancement results significantly improve accuracy in thermal images and defect profile reconstruction.The experimental results demonstrate the feasibility of the proposed method by attaining high accuracy with optimal loss norm for defect profile reconstruction with a Recall score over 0.92.The scalability investigation of different materials and defect types is also discussed,highlighting its capability for diverse thermography quantification and automated inspection scenarios.展开更多
We report the effect of boron (nitrogen)-divacancy complex defects on the electronic properties of graphene nanoribbon by means of density functional theory. It is found that the defective subbands appear in the condu...We report the effect of boron (nitrogen)-divacancy complex defects on the electronic properties of graphene nanoribbon by means of density functional theory. It is found that the defective subbands appear in the conduction band and valence band in accordance with boron (nitrogen)-divacancy defect, respectively;the impurity subbands don’t lead to the transition from the metallic characteristic to a semiconducting one. These complex defects affect the electronic band structures around the Fermi level of the graphene nanoribbon;the charge densities of these configurations have also changed distinctly. It is hoped that the theoretical results are helpful in designing the electronic device.展开更多
Gallium （Ga）-doped ZnO is regarded as a promising plasmonic material with a wide range of applications in plasmonics. In this study, zinc self-diffusion experiments are adopted to disclose the nature of the dominant...Gallium （Ga）-doped ZnO is regarded as a promising plasmonic material with a wide range of applications in plasmonics. In this study, zinc self-diffusion experiments are adopted to disclose the nature of the dominant compensating defect in Ga-doped ZnO isotopic heterostructures. The （GaZn-VZ.）- complex defect, instead of the isolated VZn^2-, is identified as the predominant compensating acceptor center responsible for the low donor doping efficiency. The comparative diffusion experiments operated by the secondary ion mass spectrometry reveal a -0.78 eV binding energy of this complex defect, which well matches the electrical activation energy derived from the temperature-dependent Hall effect measurements （-（0.82±0.02） eV）. These findings contribute to an essential understanding of the （GaZn-VZn）- complex defect and the potential engineering routes of heavily Ga-doped ZnO.展开更多
Complicated and large acetabular bone defects present the main challenges and difficulty in the revision of total hip arthroplasty(THA).This study aimed to explore the advantages of three-dimensional(3D)printing techn...Complicated and large acetabular bone defects present the main challenges and difficulty in the revision of total hip arthroplasty(THA).This study aimed to explore the advantages of three-dimensional(3D)printing technology in the reconstruction of such acetabular bone defects.We retrospectively analyzed the prognosis of four severe bone defects around the acetabulum in three patients who were treated using 3D printing technology.Reconstruction of bone defect by conventional methods was difficult in these patients.In this endeavor,we used radiographic methods,related computer software such as Materialise's interactive medical image control system and Siemens NX software,and actual surgical experience to estimate defect volume,prosthesis stability,and installation accuracy,respectively.Moreover,a Harris hip score was obtained to evaluate limb function.It was found that bone defects could be adequately reconstructed using a 3D printing prosthesis,and its stability was reliable.The Harris hip score indicated a very good functional recovery in all three patients.In conclusion,3D printing technology had a good therapeutic effect on both complex and large bone defects in the revision of THA.It was able to achieve good curative effects in patients with large bone defects.展开更多
We present first-principles calculations of the formation energy of different native defects and their complexes in wurtzite InN using density-functional theory and the pseudopotential plane-wave method. Our calculati...We present first-principles calculations of the formation energy of different native defects and their complexes in wurtzite InN using density-functional theory and the pseudopotential plane-wave method. Our calculations are aimed in the three cases： N/In = 1, N/In 〉 1 （N-rich）, and N/In 〈 1 （In-rich）. Our results indicate that the antisite defect has the lowest formation energy under N/In = 1. The formation energy of nitrogen interstitial （nitrogen vacancy） defect is significantly low under the N-rich （In-rich） condition. Thus the antisite defect is an important defect if N/In = 1, and the nitrogen interstitial （nitrogen vacancy） defect is a vital defect under the N-rich （In-rich） condition. The atomic site relaxation around the nitrogen interstitial and vacancy is investigated. Our calculations show that the nitrogen vacancy cannot be observed although it is one of the most important defects in InN. Our results are confirmed by experiments.展开更多
In this paper, the X-ray nondestructive test method of small defects in precision weldments with complex structure was presented. To resolve the difficulty of defect segmentation in variable grey image, the image proc...In this paper, the X-ray nondestructive test method of small defects in precision weldments with complex structure was presented. To resolve the difficulty of defect segmentation in variable grey image, the image processing based on Visual Basic programming method was adopted. The methods of automatic contrast and partial grey stretch were used to enhance the X-ray detection image which has relatively low contrast, then automatic threshold method was carried out to segment the two high intensity zones, and weld zones which contain the small defects was extracted. Smoothing and sharpen processing were proceeded on the extracted weld zones, and small defects in X-ray detection image of weldments with complex structure were segmented by using the method of background subtraction in the end. The effects of raster were eliminated, and because of that the image processing was only proceeded on the extracted weld zones, the calculated speed using the above provided algorithm was improved.展开更多
To extract features of fabric defects effectively and reduce dimension of feature space,a feature extraction method of fabric defects based on complex contourlet transform （CCT） and principal component analysis （PC...To extract features of fabric defects effectively and reduce dimension of feature space,a feature extraction method of fabric defects based on complex contourlet transform （CCT） and principal component analysis （PCA） is proposed.Firstly,training samples of fabric defect images are decomposed by CCT.Secondly,PCA is applied in the obtained low-frequency component and part of highfrequency components to get a lower dimensional feature space.Finally,components of testing samples obtained by CCT are projected onto the feature space where different types of fabric defects are distinguished by the minimum Euclidean distance method.A large number of experimental results show that,compared with PCA,the method combining wavdet low-frequency component with PCA （WLPCA）,the method combining contourlet transform with PCA （CPCA）,and the method combining wavelet low-frequency and highfrequency components with PCA （WPCA）,the proposed method can extract features of common fabric defect types effectively.The recognition rate is greatly improved while the dimension is reduced.展开更多
基于计算机视觉的航拍绝缘子缺陷检测方法被广泛应用于电力巡检。针对绝缘子缺陷易受背景复杂、目标尺度较小等因素的影响而导致漏检、误检的问题,提出了一种旨在提高绝缘子缺陷检测精度的绝缘子缺陷检测模型YOLO-insulator。首先,引入...基于计算机视觉的航拍绝缘子缺陷检测方法被广泛应用于电力巡检。针对绝缘子缺陷易受背景复杂、目标尺度较小等因素的影响而导致漏检、误检的问题,提出了一种旨在提高绝缘子缺陷检测精度的绝缘子缺陷检测模型YOLO-insulator。首先,引入基于通道混洗的重参数化卷积(reparameterized convolution based on channel shuffle-one-shot aggregation, RCS-OSA)替换传统的二维卷积C2f,以增强网络的特征提取能力;其次,在颈部网络使用RCS-OSA模块替换部分的C2f卷积,同时引入挤压激励网络(squeeze and excitation network,SENet),以增强模型对通道间关系的捕捉和整体特征的表达能力;最后,针对多种缺陷区域小导致难以检测的问题,提出小目标检测层方法,该层包含更多的缺陷细节信息,有利于缺陷的检测。在自制绝缘子数据集上进行实验验证的结果表明,相对于基线YOLOv8n,YOLO-insulator模型在查准率、召回率、平均精度均值上都实现了提升,有效提高了模型的综合性能。展开更多
Objective:The aim of the study was to present our experience in reconstruction of complex defects of the nose.Methods:Fourteen patients presenting with large composite defects of the nose were anatomically reconstruct...Objective:The aim of the study was to present our experience in reconstruction of complex defects of the nose.Methods:Fourteen patients presenting with large composite defects of the nose were anatomically reconstructed after full tumor clearance of a skin cancer.The aesthetic outcome was assessed subjectively and objectively while the functional outcome was only assessed subjectively in 13 patients.Results:Basal cell carcinoma(BCC),represented the tumor excised in 10 patients while the remaining 4 patients suffered from squamous cell carcinoma(SCC).One patient died of extensive local recurrence of SCC after 6 months.The commonest flap used for inner lining was the septal flap while the forehead paramedian flap provided the external coverage for the majority of patients.All flaps survived completely except in one patient who developed distal paramedian forehead flap necrosis.Two patients developed multiple abscesses and sinuses discharging parts of cartilage grafts through the flaps’skin with one patient suffering from total extrusion of the costal cartilage grafts.Two other patients suffered from severe nostril stenosis.All patients had variable degree of difficulty in airway passage,while most patients were satisfied with the total nasal appearance.The objective assessment of the overall appearance of the nose scored less than the subjective satisfaction.Conclusion:Reconstruction of complex nasal defects has a high learning curve.Intranasal flaps are usually of limited size and nostril asymmetry is likely to occur.Local or regional skin flaps if available are still considered a good choice for inner as well as outer lining.展开更多
Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge struct...Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti^3＋-V O defect complexes（or clusters） have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti^3＋ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.展开更多
The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemi...The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.展开更多
This paper investigates the infrared absorption spectra of oxygen-related complexes in silicon crystals irradiated with electron （1.5 MeV） at 360 K.Two groups of samples with low [Oi] = 6.9 x 10^17 cm^-3 and high [O...This paper investigates the infrared absorption spectra of oxygen-related complexes in silicon crystals irradiated with electron （1.5 MeV） at 360 K.Two groups of samples with low [Oi] = 6.9 x 10^17 cm^-3 and high [Oi] = 1.06 x 10^18 cm^-3 were used.We found that the concentration of the VO pairs have different behaviour to the annealing temperature in different concentration of oxygen specimen,it is hardly changed in the higher concentration of oxygen specimen.It was also found that the concentration of VO2 in lower concentration of oxygen specimen gets to maximum at 450 ℃ and then dissapears at 500 ℃,accompanied with the appearing of VO3. For both kinds of specimens,the concentration of VO3 reachs to maximum at 550 ℃ and does not disappear completely at 600 ℃.展开更多
We investigate the flow induced by annihilation of a pair of defects in liquid crystals using the Doi theory with the Marrucci-Greco potential, in which the orientation state is described with the orientational distri...We investigate the flow induced by annihilation of a pair of defects in liquid crystals using the Doi theory with the Marrucci-Greco potential, in which the orientation state is described with the orientational distribution function. We have numerically studied both the transient behaviors of two defects with different structures and their velocity field, and estimated the magnitude of the induced velocity. A defect with positive strength moves faster than one with negative strength. The long-range order of the molecular orientation field has a large effect on the annihilation time, and the annihilation time is reduced by increasing the long-range order. We find that flows are induced during the annihilation of a pair of defects and that several vortices are generated in the vicinity of the defects. The maximum velocity is predicted to develop spatially between the two defects just after their annihilation in time. In our simulation, the maximum induced velocity reaches an order of 10 μm/s. The induced velocity increases with increasing long range-order and nematic potential strength.展开更多
基金supported by the UK EPSRC Platform Grant:Through-life performance:From science to instrumentation(Grant No.EP/P027121/1).
文摘Although machine Learning has demonstrated exceptional applicability in thermographic inspection,precise defect reconstruction is still challenging,especially for complex defect profiles with limited defect sample diversity.Thus,this paper proposes a self-enhancement defect reconstruction technique based on cycle-consistent generative adversarial network(Cycle-GAN)that accurately characterises complex defect profiles and generates reliable artificial thermal images for dataset augmentation,enhancing defect characterisation.By using a synthetic dataset from simulation and experiments,the network overcomes the limited samples problem by learning the diversity of complex defects from finite element modelling and obtaining the thermography uncertainty patterns from practical experiments.Then,an iterative strategy with a self-enhancement capability optimises the characterisation accuracy and data generation performance.The designed loss function structure with cycle consistency and identity loss constrains the GAN’s transfer variation to guarantee augmented data quality and defect reconstruction accuracy simultaneously,while the self-enhancement results significantly improve accuracy in thermal images and defect profile reconstruction.The experimental results demonstrate the feasibility of the proposed method by attaining high accuracy with optimal loss norm for defect profile reconstruction with a Recall score over 0.92.The scalability investigation of different materials and defect types is also discussed,highlighting its capability for diverse thermography quantification and automated inspection scenarios.
文摘We report the effect of boron (nitrogen)-divacancy complex defects on the electronic properties of graphene nanoribbon by means of density functional theory. It is found that the defective subbands appear in the conduction band and valence band in accordance with boron (nitrogen)-divacancy defect, respectively;the impurity subbands don’t lead to the transition from the metallic characteristic to a semiconducting one. These complex defects affect the electronic band structures around the Fermi level of the graphene nanoribbon;the charge densities of these configurations have also changed distinctly. It is hoped that the theoretical results are helpful in designing the electronic device.
基金supported by the National Natural Science Foundation of China(Grants Nos.11674405,and 11675280)
文摘Gallium （Ga）-doped ZnO is regarded as a promising plasmonic material with a wide range of applications in plasmonics. In this study, zinc self-diffusion experiments are adopted to disclose the nature of the dominant compensating defect in Ga-doped ZnO isotopic heterostructures. The （GaZn-VZ.）- complex defect, instead of the isolated VZn^2-, is identified as the predominant compensating acceptor center responsible for the low donor doping efficiency. The comparative diffusion experiments operated by the secondary ion mass spectrometry reveal a -0.78 eV binding energy of this complex defect, which well matches the electrical activation energy derived from the temperature-dependent Hall effect measurements （-（0.82±0.02） eV）. These findings contribute to an essential understanding of the （GaZn-VZn）- complex defect and the potential engineering routes of heavily Ga-doped ZnO.
基金This work is supported by National Key Research and Development Program of China(2016YFC1100600)the National Natural Science Foundation of China(81972058 and 81902194)the Multicenter Clinical Research Project of Shanghai Jiao Tong University School of Medicine(DLY201506).
文摘Complicated and large acetabular bone defects present the main challenges and difficulty in the revision of total hip arthroplasty(THA).This study aimed to explore the advantages of three-dimensional(3D)printing technology in the reconstruction of such acetabular bone defects.We retrospectively analyzed the prognosis of four severe bone defects around the acetabulum in three patients who were treated using 3D printing technology.Reconstruction of bone defect by conventional methods was difficult in these patients.In this endeavor,we used radiographic methods,related computer software such as Materialise's interactive medical image control system and Siemens NX software,and actual surgical experience to estimate defect volume,prosthesis stability,and installation accuracy,respectively.Moreover,a Harris hip score was obtained to evaluate limb function.It was found that bone defects could be adequately reconstructed using a 3D printing prosthesis,and its stability was reliable.The Harris hip score indicated a very good functional recovery in all three patients.In conclusion,3D printing technology had a good therapeutic effect on both complex and large bone defects in the revision of THA.It was able to achieve good curative effects in patients with large bone defects.
基金Supported by the National Basic Research Program of China under Grant No. 2006CB921607the National Natural Science Foundation of China under Grant Nos. 60711120203, 60890193+1 种基金the Natural Science Foundation of Beijing City under Grant No. 1092007the Science and Technology Research Foundation for Colleges and Universities of Inner Mongolia Autonomous Region under Grant No. NJ09026
文摘We present first-principles calculations of the formation energy of different native defects and their complexes in wurtzite InN using density-functional theory and the pseudopotential plane-wave method. Our calculations are aimed in the three cases： N/In = 1, N/In 〉 1 （N-rich）, and N/In 〈 1 （In-rich）. Our results indicate that the antisite defect has the lowest formation energy under N/In = 1. The formation energy of nitrogen interstitial （nitrogen vacancy） defect is significantly low under the N-rich （In-rich） condition. Thus the antisite defect is an important defect if N/In = 1, and the nitrogen interstitial （nitrogen vacancy） defect is a vital defect under the N-rich （In-rich） condition. The atomic site relaxation around the nitrogen interstitial and vacancy is investigated. Our calculations show that the nitrogen vacancy cannot be observed although it is one of the most important defects in InN. Our results are confirmed by experiments.
文摘In this paper, the X-ray nondestructive test method of small defects in precision weldments with complex structure was presented. To resolve the difficulty of defect segmentation in variable grey image, the image processing based on Visual Basic programming method was adopted. The methods of automatic contrast and partial grey stretch were used to enhance the X-ray detection image which has relatively low contrast, then automatic threshold method was carried out to segment the two high intensity zones, and weld zones which contain the small defects was extracted. Smoothing and sharpen processing were proceeded on the extracted weld zones, and small defects in X-ray detection image of weldments with complex structure were segmented by using the method of background subtraction in the end. The effects of raster were eliminated, and because of that the image processing was only proceeded on the extracted weld zones, the calculated speed using the above provided algorithm was improved.
基金National Natural Science Foundation of China(No.60872065)the Key Laboratory of Textile Science&Technology,Ministry of Education,China(No.P1111)+1 种基金the Key Laboratory of Advanced Textile Materials and Manufacturing Technology,Ministry of Education,China(No.2010001)the Priority Academic Program Development of Jiangsu Higher Education Institution,China
文摘To extract features of fabric defects effectively and reduce dimension of feature space,a feature extraction method of fabric defects based on complex contourlet transform （CCT） and principal component analysis （PCA） is proposed.Firstly,training samples of fabric defect images are decomposed by CCT.Secondly,PCA is applied in the obtained low-frequency component and part of highfrequency components to get a lower dimensional feature space.Finally,components of testing samples obtained by CCT are projected onto the feature space where different types of fabric defects are distinguished by the minimum Euclidean distance method.A large number of experimental results show that,compared with PCA,the method combining wavdet low-frequency component with PCA （WLPCA）,the method combining contourlet transform with PCA （CPCA）,and the method combining wavelet low-frequency and highfrequency components with PCA （WPCA）,the proposed method can extract features of common fabric defect types effectively.The recognition rate is greatly improved while the dimension is reduced.
文摘基于计算机视觉的航拍绝缘子缺陷检测方法被广泛应用于电力巡检。针对绝缘子缺陷易受背景复杂、目标尺度较小等因素的影响而导致漏检、误检的问题,提出了一种旨在提高绝缘子缺陷检测精度的绝缘子缺陷检测模型YOLO-insulator。首先,引入基于通道混洗的重参数化卷积(reparameterized convolution based on channel shuffle-one-shot aggregation, RCS-OSA)替换传统的二维卷积C2f,以增强网络的特征提取能力;其次,在颈部网络使用RCS-OSA模块替换部分的C2f卷积,同时引入挤压激励网络(squeeze and excitation network,SENet),以增强模型对通道间关系的捕捉和整体特征的表达能力;最后,针对多种缺陷区域小导致难以检测的问题,提出小目标检测层方法,该层包含更多的缺陷细节信息,有利于缺陷的检测。在自制绝缘子数据集上进行实验验证的结果表明,相对于基线YOLOv8n,YOLO-insulator模型在查准率、召回率、平均精度均值上都实现了提升,有效提高了模型的综合性能。
文摘Objective:The aim of the study was to present our experience in reconstruction of complex defects of the nose.Methods:Fourteen patients presenting with large composite defects of the nose were anatomically reconstructed after full tumor clearance of a skin cancer.The aesthetic outcome was assessed subjectively and objectively while the functional outcome was only assessed subjectively in 13 patients.Results:Basal cell carcinoma(BCC),represented the tumor excised in 10 patients while the remaining 4 patients suffered from squamous cell carcinoma(SCC).One patient died of extensive local recurrence of SCC after 6 months.The commonest flap used for inner lining was the septal flap while the forehead paramedian flap provided the external coverage for the majority of patients.All flaps survived completely except in one patient who developed distal paramedian forehead flap necrosis.Two patients developed multiple abscesses and sinuses discharging parts of cartilage grafts through the flaps’skin with one patient suffering from total extrusion of the costal cartilage grafts.Two other patients suffered from severe nostril stenosis.All patients had variable degree of difficulty in airway passage,while most patients were satisfied with the total nasal appearance.The objective assessment of the overall appearance of the nose scored less than the subjective satisfaction.Conclusion:Reconstruction of complex nasal defects has a high learning curve.Intranasal flaps are usually of limited size and nostril asymmetry is likely to occur.Local or regional skin flaps if available are still considered a good choice for inner as well as outer lining.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61006066)the National Natural Science Foundation of China (Grant No. 11175191)
文摘Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti^3＋-V O defect complexes（or clusters） have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti^3＋ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.
基金Project supported by the Ministry of Science and Technology of China (No.2001BA803B03-05).
文摘The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.
基金Project supported by the National Natural Science Foundation of China (Grant No 50872028)Natural Science Foundation of Hebei Province of China (Grant Nos E200500048 and E2008000079)Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20050080006)
文摘This paper investigates the infrared absorption spectra of oxygen-related complexes in silicon crystals irradiated with electron （1.5 MeV） at 360 K.Two groups of samples with low [Oi] = 6.9 x 10^17 cm^-3 and high [Oi] = 1.06 x 10^18 cm^-3 were used.We found that the concentration of the VO pairs have different behaviour to the annealing temperature in different concentration of oxygen specimen,it is hardly changed in the higher concentration of oxygen specimen.It was also found that the concentration of VO2 in lower concentration of oxygen specimen gets to maximum at 450 ℃ and then dissapears at 500 ℃,accompanied with the appearing of VO3. For both kinds of specimens,the concentration of VO3 reachs to maximum at 550 ℃ and does not disappear completely at 600 ℃.
文摘We investigate the flow induced by annihilation of a pair of defects in liquid crystals using the Doi theory with the Marrucci-Greco potential, in which the orientation state is described with the orientational distribution function. We have numerically studied both the transient behaviors of two defects with different structures and their velocity field, and estimated the magnitude of the induced velocity. A defect with positive strength moves faster than one with negative strength. The long-range order of the molecular orientation field has a large effect on the annihilation time, and the annihilation time is reduced by increasing the long-range order. We find that flows are induced during the annihilation of a pair of defects and that several vortices are generated in the vicinity of the defects. The maximum velocity is predicted to develop spatially between the two defects just after their annihilation in time. In our simulation, the maximum induced velocity reaches an order of 10 μm/s. The induced velocity increases with increasing long range-order and nematic potential strength.
