The rigid, perfectly plastic dynamic response of a free-free beam subjected to impact by a projectile at any cross-section is studied. The instantaneous deformations of the beam are given through an analysis of the ...The rigid, perfectly plastic dynamic response of a free-free beam subjected to impact by a projectile at any cross-section is studied. The instantaneous deformations of the beam are given through an analysis of the complete solution for rigid plastic structures. The in?uence of some parameters such as the input energy and mass ratio on the plastic deformation, travelling plastic hinge position and energy partitioning of the beam are discussed.展开更多
A series of In Sb thin films were grown on Ga As substrates by molecular beam epitaxy(MBE).Ga Sb/Al In Sb is used as a compound buffer layer to release the strain caused by the lattice mismatch between the substrate a...A series of In Sb thin films were grown on Ga As substrates by molecular beam epitaxy(MBE).Ga Sb/Al In Sb is used as a compound buffer layer to release the strain caused by the lattice mismatch between the substrate and the epitaxial layer,so as to reduce the system defects.At the same time,the influence of different interface structures of Al In Sb on the surface morphology of buffer layer is explored.The propagation mechanism of defects with the growth of buffer layer is compared and analyzed.The relationship between the quality of In Sb thin films and the structure of buffer layer is summarized.Finally,the growth of high quality In Sb thin films is realized.展开更多
The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode(WBE). The electrochemical impedance spectroscopy(EIS) of the W...The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode(WBE). The electrochemical impedance spectroscopy(EIS) of the WBE was carried out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.展开更多
BACKGROUND Hip revision surgery is the final treatment option for the failure of artificial hip joints, but it is more difficult than the initial operation. For patients with hip joint loosening around the prosthesis ...BACKGROUND Hip revision surgery is the final treatment option for the failure of artificial hip joints, but it is more difficult than the initial operation. For patients with hip joint loosening around the prosthesis combined with large inflammatory pseudotumours and large segment bone defects, hip revision is even more difficult, and clinical reports are rare.CASE SUMMARY Male, 59 years old. The patient underwent left hip replacement 35 years ago and was now admitted to hospital due to massive masses in the left thigh, shortening of the left lower extremity, and pain and lameness of the left hip joint. X-ray, computed tomography and magnetic resonance imaging revealed prosthesis loosening, left acetabular bone defect(Parprosky IIIB type), and a bone defect of the left proximal femur(Parprosky IIIA type). Inflammatory pseudotumours were seen in the left hip and left thigh. Hip revision surgery was performed using a 3Dprinted custom acetabular prosthesis was used for hip revision surgery, which was produced by Arcam Electron Beam Melting system with Electron Beam Melting technology. The operation was successful, and the patient was followed up regularly after the operation. The custom-made acetabular prosthesis was well matched, the inflammatory pseudotumour was completely removed, the postoperative hip prosthesis was stable, and the old greater trochanter fracture was well reduced and fixed. The patient was partially weight-bearing with crutches 3 mo after the operation and walked with full weight-bearing after 6 mo. The hip prosthesis was stable, and there was no recurrence of inflammatory pseudotumours at the last follow-up. The Visual Analogue Scale was 3, and the Harris hip score was 90.CONCLUSION The use of 3D-printed personalized custom prostheses for complex hip revision surgery has satisfactory surgical results and has great clinical application value.展开更多
Apeculiar crystal defect was observed by experiment of high resolution electron microscopy( HREM) .It wasidentifiedtoformed bytwothreading dislocationsand asegmentof(11 20) domain boundary. An atomicstructure model wa...Apeculiar crystal defect was observed by experiment of high resolution electron microscopy( HREM) .It wasidentifiedtoformed bytwothreading dislocationsand asegmentof(11 20) domain boundary. An atomicstructure model was proposed for the anomalous defect. Theresultofthe weak beam experimentofelectron microscopeaffirmedthesuggested model.Thestructuralpropertiesofseveral GaN(11 2 0) domain boundaries werestudied by Molec ular Dynamicscalculations. Thetheoreticalresultsshowedthatthelike atom bonding domain boundary, whichcomposesthe main partofthe peculiar defect, has much higher formationenergy than itcounterpartof unlike atom bonding domain boundary. Theoutcome providesanotherevidenceforthesuggested model.展开更多
This paper addresses the studies carried out on an I-beam to reveal the wave propagation characteristics and tackle the multi-mode propagation of Lamb waves. The experimental setup consisted of a new 3D Scanning Laser...This paper addresses the studies carried out on an I-beam to reveal the wave propagation characteristics and tackle the multi-mode propagation of Lamb waves. The experimental setup consisted of a new 3D Scanning Laser Doppler Vibrometer manufactured by Polytec (3D-SLDV) and was used to acquire high resolution time-space Lamb waves that were propagating in the I-beam. A high power and pulsed Nd:YAG laser was used to emit the required Lamb waves. The emission and sensing of the waves were carried out simultaneously. The wave propagation data was recorded by scanning the surface of the I-beam in a sequential manner. The measured data was used to construct the wave patterns that were propagating in the I-beams at different time instants. Furthermore, as the waves in an I-Beam propagate with multiple modes even at low frequency range, filtering was carried out in the frequency-wavenum- ber domain in order to decompose the modes. The results presented thereby confirm that the new 3D-SLDV possesses tremendous capability in revealing the wave propagation characteristics and its interaction with defect. The results could be the first time that the waves propagating in a real I-beam can be visually observed, whilst in the past, it can only be visualized through simulation. The capability of using such totally laser-based 3D inspection system to reveal the characteristics of Lamb wave and its interaction with defects are substantial.展开更多
The laser-induced damage threshold(LIDT)of plate laser beam splitter(PLBS)coatings is closely related to the subsurface absorption defects of the substrate.Herein,a two-step deposition temperature method is proposed t...The laser-induced damage threshold(LIDT)of plate laser beam splitter(PLBS)coatings is closely related to the subsurface absorption defects of the substrate.Herein,a two-step deposition temperature method is proposed to understand the effect of substrate subsurface impurity defects on the LIDT of PLBS coatings.Firstly,BK7 substrates are heat-treated at three different temperatures.The surface morphology and subsurface impurity defect distribution of the substrate before and after the heat treatment are compared.Then,a PLBS coating consisting of alternating HfO2–Al2O3 mixture and SiO2 layers is designed to achieve a beam-splitting ratio(transmittance to reflectance,s-polarized light)of approximately 50:50 at 1053 nm and an angle of incidence of 45◦,and it is prepared under four different deposition processes.The experimental and simulation results show that the subsurface impurity defects of the substrate migrate to the surface and accumulate on the surface during the heat treatment,and become absorption defect sources or nodule defect seeds in the coating,reducing the LIDT of the coating.The higher the heat treatment temperature,the more evident the migration and accumulation of impurity defects.A lower deposition temperature(at which the coating can be fully oxidized)helps to improve the LIDT of the PLBS coating.When the deposition temperature is 140◦C,the LIDT(s-polarized light,wavelength:1064 nm,pulse width:9 ns,incident angle:45◦)of the PLBS coating is 26.2 J/cm2,which is approximately 6.7 times that of the PLBS coating deposited at 200◦C.We believe that the investigation into the laser damage mechanism of PLBS coatings will help to improve the LIDT of coatings with partial or high transmittance at laser wavelengths.展开更多
基金Project supported by the National Natural Science Foundation of China (No.10272011).
文摘The rigid, perfectly plastic dynamic response of a free-free beam subjected to impact by a projectile at any cross-section is studied. The instantaneous deformations of the beam are given through an analysis of the complete solution for rigid plastic structures. The in?uence of some parameters such as the input energy and mass ratio on the plastic deformation, travelling plastic hinge position and energy partitioning of the beam are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61774130,11474248,61790581,and 51973070)the Ph.D.Program Foundation of the Ministry of Education of China(Grant No.20105303120002)the National Key Technology Research and Development Program of China(Grant No.2018YFA0209101)。
文摘A series of In Sb thin films were grown on Ga As substrates by molecular beam epitaxy(MBE).Ga Sb/Al In Sb is used as a compound buffer layer to release the strain caused by the lattice mismatch between the substrate and the epitaxial layer,so as to reduce the system defects.At the same time,the influence of different interface structures of Al In Sb on the surface morphology of buffer layer is explored.The propagation mechanism of defects with the growth of buffer layer is compared and analyzed.The relationship between the quality of In Sb thin films and the structure of buffer layer is summarized.Finally,the growth of high quality In Sb thin films is realized.
基金supported by the National Natural Science Foundation of China (Grant No. 51131005)
文摘The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode(WBE). The electrochemical impedance spectroscopy(EIS) of the WBE was carried out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.
文摘BACKGROUND Hip revision surgery is the final treatment option for the failure of artificial hip joints, but it is more difficult than the initial operation. For patients with hip joint loosening around the prosthesis combined with large inflammatory pseudotumours and large segment bone defects, hip revision is even more difficult, and clinical reports are rare.CASE SUMMARY Male, 59 years old. The patient underwent left hip replacement 35 years ago and was now admitted to hospital due to massive masses in the left thigh, shortening of the left lower extremity, and pain and lameness of the left hip joint. X-ray, computed tomography and magnetic resonance imaging revealed prosthesis loosening, left acetabular bone defect(Parprosky IIIB type), and a bone defect of the left proximal femur(Parprosky IIIA type). Inflammatory pseudotumours were seen in the left hip and left thigh. Hip revision surgery was performed using a 3Dprinted custom acetabular prosthesis was used for hip revision surgery, which was produced by Arcam Electron Beam Melting system with Electron Beam Melting technology. The operation was successful, and the patient was followed up regularly after the operation. The custom-made acetabular prosthesis was well matched, the inflammatory pseudotumour was completely removed, the postoperative hip prosthesis was stable, and the old greater trochanter fracture was well reduced and fixed. The patient was partially weight-bearing with crutches 3 mo after the operation and walked with full weight-bearing after 6 mo. The hip prosthesis was stable, and there was no recurrence of inflammatory pseudotumours at the last follow-up. The Visual Analogue Scale was 3, and the Harris hip score was 90.CONCLUSION The use of 3D-printed personalized custom prostheses for complex hip revision surgery has satisfactory surgical results and has great clinical application value.
文摘Apeculiar crystal defect was observed by experiment of high resolution electron microscopy( HREM) .It wasidentifiedtoformed bytwothreading dislocationsand asegmentof(11 20) domain boundary. An atomicstructure model was proposed for the anomalous defect. Theresultofthe weak beam experimentofelectron microscopeaffirmedthesuggested model.Thestructuralpropertiesofseveral GaN(11 2 0) domain boundaries werestudied by Molec ular Dynamicscalculations. Thetheoreticalresultsshowedthatthelike atom bonding domain boundary, whichcomposesthe main partofthe peculiar defect, has much higher formationenergy than itcounterpartof unlike atom bonding domain boundary. Theoutcome providesanotherevidenceforthesuggested model.
文摘This paper addresses the studies carried out on an I-beam to reveal the wave propagation characteristics and tackle the multi-mode propagation of Lamb waves. The experimental setup consisted of a new 3D Scanning Laser Doppler Vibrometer manufactured by Polytec (3D-SLDV) and was used to acquire high resolution time-space Lamb waves that were propagating in the I-beam. A high power and pulsed Nd:YAG laser was used to emit the required Lamb waves. The emission and sensing of the waves were carried out simultaneously. The wave propagation data was recorded by scanning the surface of the I-beam in a sequential manner. The measured data was used to construct the wave patterns that were propagating in the I-beams at different time instants. Furthermore, as the waves in an I-Beam propagate with multiple modes even at low frequency range, filtering was carried out in the frequency-wavenum- ber domain in order to decompose the modes. The results presented thereby confirm that the new 3D-SLDV possesses tremendous capability in revealing the wave propagation characteristics and its interaction with defect. The results could be the first time that the waves propagating in a real I-beam can be visually observed, whilst in the past, it can only be visualized through simulation. The capability of using such totally laser-based 3D inspection system to reveal the characteristics of Lamb wave and its interaction with defects are substantial.
基金This study was supported by the National Natural Science Foundation of China(61975215)Youth Innovation Promotion Association of the Chinese Academy of Sciences,Strategic Priority Research Program of the Chinese Academy of Sciences(XDA25020206)the Science and Technology Planning Project of Shanghai Municipal Science&Technology Commission(21DZ1100400).
文摘The laser-induced damage threshold(LIDT)of plate laser beam splitter(PLBS)coatings is closely related to the subsurface absorption defects of the substrate.Herein,a two-step deposition temperature method is proposed to understand the effect of substrate subsurface impurity defects on the LIDT of PLBS coatings.Firstly,BK7 substrates are heat-treated at three different temperatures.The surface morphology and subsurface impurity defect distribution of the substrate before and after the heat treatment are compared.Then,a PLBS coating consisting of alternating HfO2–Al2O3 mixture and SiO2 layers is designed to achieve a beam-splitting ratio(transmittance to reflectance,s-polarized light)of approximately 50:50 at 1053 nm and an angle of incidence of 45◦,and it is prepared under four different deposition processes.The experimental and simulation results show that the subsurface impurity defects of the substrate migrate to the surface and accumulate on the surface during the heat treatment,and become absorption defect sources or nodule defect seeds in the coating,reducing the LIDT of the coating.The higher the heat treatment temperature,the more evident the migration and accumulation of impurity defects.A lower deposition temperature(at which the coating can be fully oxidized)helps to improve the LIDT of the PLBS coating.When the deposition temperature is 140◦C,the LIDT(s-polarized light,wavelength:1064 nm,pulse width:9 ns,incident angle:45◦)of the PLBS coating is 26.2 J/cm2,which is approximately 6.7 times that of the PLBS coating deposited at 200◦C.We believe that the investigation into the laser damage mechanism of PLBS coatings will help to improve the LIDT of coatings with partial or high transmittance at laser wavelengths.
