AIM： TO determine if a nasojejunal tube （NJT） is required for optimal examination of enteroclysis and if patients can be examined only in the supine position. METHODS： Data were collected from all patients undergo...AIM： TO determine if a nasojejunal tube （NJT） is required for optimal examination of enteroclysis and if patients can be examined only in the supine position. METHODS： Data were collected from all patients undergoing small bowel （SB） magnetic resonance imaging （MRI） examination over a 32-mo period. Patients either underwent a magnetic resonance （MR） follow-through （MRFT） or a MR enteroclysis （MRE） in the supine position. The quality of proximal and distal SB distension as well as the presence of motion artefact and image quality were assessed by 2 radiologists. RESULTS： One hundred and fourteen MR studies were undertaken （MRFT-49, MRE-65） in 108 patients in the supine position only. Image artefact was more frequent in MRE than in MRFT （29.2% vs 18.4%）, but was not statistically significant （P = 0.30）. Adequate distension of the distal SB was obtained in 97.8% of MRFT examinations and in 95.4% of MRE examinations, respectively. Proximal SB distension was, however, less frequently optimal in MRFT than in MRE （P = 0.0036）, particularly in patients over the age of 50 years （P = 0.0099）. Image quality was good in all examinations. CONCLUSION： All patients could be successfully iraaged in the supine position. MRE and MRFT are equivalent for distal SB distension and artefact effects. Proximal SB distension is frequently less optimal in MRFT than in MRE. MRE is, therefore, the preferred MR examination method of the SB.展开更多
In order to develop skin artefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone nlbber and knitted nylon sheet were selected to manufacture an artific...In order to develop skin artefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone nlbber and knitted nylon sheet were selected to manufacture an artificial skin, due to their higher elastic strain and high flexibility. Tensile and scissors cutting tests were conducted to characterise the matrix and reinforcing materials and the skin artefact. Material properties of the individual and the composite materials were compared with the measured properties of real octopus skin presented ill Part I. The Young＇s modulus of the skin should be below 20 MPa and the elastic strain range should be over 60%. The fracture toughness should be at least 0.9 kJ.m 2. Tubes made of the skin artefact filled with liquid were tested to study volume change under deformation. Finite element analysis model was developed to simulate the material and arm structure under tensile loading. Results show that the skin artefact developed has similar mechanical properties as the real octopus skin and satisfies all the design specifications of the OCTOPUS robot.展开更多
In order to fabricate a biomimetic skin for an octopus inspired robot, a new process was developed based on mechanical properties measured from real octopus skin. Various knitted nylon textiles were tested and the one...In order to fabricate a biomimetic skin for an octopus inspired robot, a new process was developed based on mechanical properties measured from real octopus skin. Various knitted nylon textiles were tested and the one of 10-denier nylon was chosen as reinforcement. A combination of Ecoflex 0030 and 0010 silicone rubbers was used as matrix of the composite to obtain the right stiffness for the skin-analogue system. The open mould fabrication process developed allows air bubble to escape easily and the artificial skin produced was thin and waterproof. Material properties of the biomimetic skin were char- acterised using static tensile and instrumented scissors cutting tests. The Young＇s moduli of the artificial skin are 0.08 MPa and 0.13 MPa in the longitudinal and transverse directions, which are much lower than those of the octopus skin. The strength and fracture toughness of the artificial skin, on the other hand are higher than those of real octopus skins. Conically-shaped skin prototypes to be used to cover the robotic arm unit were manufactured and tested. The biomimetic skin prototype was stiff enough to maintain it conical shape when filled with water. The driving force for elongation was reduced significantly compared with previous prototypes.展开更多
Magnetic resonance elastography (MRE) allows the quantitative assessment of the stiffness of tissues based on the tissue response to oscillatory shear stress. Shear wave displacements of the tissues are encoded as pha...Magnetic resonance elastography (MRE) allows the quantitative assessment of the stiffness of tissues based on the tissue response to oscillatory shear stress. Shear wave displacements of the tissues are encoded as phase shifts and converted to stiffness (elastogram). Generally, a partial volume effect occurs when different materials are encompassed on the same voxel. In MRE, however, the partial volume effect occurs even if the voxel is filled with the same materials because wave displacements due to vibrations are spatially distributed. The purpose of this study was to investigate how the partial volume effect can affect the phase shift and the elastogram in MRE. We assumed that the partial volume effect appears only in the slice thickness direction and performed a simulation and MRE experiment with various slice thicknesses (1 - 19 mm), two types of imaging plane (coronal and axial) and two types of vibration frequency (100 and 200 Hz). The results of the simulation and the MRE experiment were similar, and indicated that the phase shift and the elastogram changed variously depending on the slice thickness, the wave pattern and the vibration frequency, even if the voxel was filled with the same material. To reduce the partial volume effect, it is necessary to perform the MRE under the following conditions: Use a wave pattern which barely causes this artefact, a smaller voxel size and a lower vibration frequency.展开更多
The existing UAV aerial image de-fog methods have low image contrast after de-fog,the difference between light and dark image is not obvious,leading to poor de-fog effect.Therefore,an aerial image de-fog enhancement m...The existing UAV aerial image de-fog methods have low image contrast after de-fog,the difference between light and dark image is not obvious,leading to poor de-fog effect.Therefore,an aerial image de-fog enhancement method based on dark channel a priori is proposed.The image variance and absolute gradient mean are combined to get the weight coefficients,and the edge pixels are smoothed by using the multiple decomposition form.The image intensity is calculated and the noise is reduced.A convolution neural network is introduced to calculate the atmospheric transmittance in haze.Based on this,dark channel prior algorithm is used to enhance the light and shade difference of aerial photography image and realise the de-fog enhancement of aerial photography image.To verify the performance of the proposed method,simulation experiments are designed which were compared with the existing methods results in better fog-removing effect,higher contrast and shorter time.展开更多
The aim of this study was to evaluate the accuracy and reproducibility of a morphological contour interpolation(MCI)based segmentation method for the volumetric measurement of bone grafts around implants.Three 3D-prin...The aim of this study was to evaluate the accuracy and reproducibility of a morphological contour interpolation(MCI)based segmentation method for the volumetric measurement of bone grafts around implants.Three 3D-printed models(one with a cylinder and two with a geometrically-complex form)were fabricated to simulate implant placement with a simultaneous guided bone regeneration(GBR)procedure.All models were scanned using a cone beam computed tomography(CBCT)instrument with the same parameters.The true volumes of the bone grafts in the models were assessed using computer-aided calculation(controls).For the test measurements,both manual and MCI-based methods were used.A comparison between the measured and true volumes was performed to evaluate the accuracy.The coefficients of variation of repeated measurements were calculated to evaluate the reproducibility.In addition,the execution time was recorded and a comparison between the two methods was performed.The high accuracy of the MCI-based method was found with differences between the measured value and actual volume,which never exceeded 7.3%.Excellent reproducibility was shown,with coefficients of variation never exceeding 1.1%.A shorter execution time was observed for the MCI-based method than for the manual method.Within the confines of this study,the MCI-based method may be suitable for volumetric measurements of grafted bone around implants.展开更多
The Lop Nur region, in the east part of Tarim Basin, was an important transportation junction between west and east,north and south Eurasia. However, previous studies on prehistoric human activity have concentrated mo...The Lop Nur region, in the east part of Tarim Basin, was an important transportation junction between west and east,north and south Eurasia. However, previous studies on prehistoric human activity have concentrated mostly on the Bronze Age,whereas that during the Stone Age remains largely unresearched. Here, we present a new direct evidence of human activity in the late Pleistocene, recorded on a grinding stone buried in a lacustrine sediment section of the Lop Nur region. The grain size distribution of the sediment section indicates that the site was probably in the center of a lake with weak hydrodynamic environment. Therefore, the stone artifact can only be carried to here by people instead of river and it was never move as soon as left here. Results of radiocarbon dating, the evident stratigraphic relations between the stone artifact and the sedimentary formation, indicate that the human activity could extend to approximately 13 ka BP. Furthermore, the results of starch-grain and use-wear analyses suggest that ancient humans gathered seeds of Triticeae, roots, and tubers and used the grinding stone to simply process selected plant as plant foodstuffs during this period. It implies that the environmental conditions in the river delta of the Lop Nur were inhabitable during the late Pleistocene.展开更多
文摘AIM： TO determine if a nasojejunal tube （NJT） is required for optimal examination of enteroclysis and if patients can be examined only in the supine position. METHODS： Data were collected from all patients undergoing small bowel （SB） magnetic resonance imaging （MRI） examination over a 32-mo period. Patients either underwent a magnetic resonance （MR） follow-through （MRFT） or a MR enteroclysis （MRE） in the supine position. The quality of proximal and distal SB distension as well as the presence of motion artefact and image quality were assessed by 2 radiologists. RESULTS： One hundred and fourteen MR studies were undertaken （MRFT-49, MRE-65） in 108 patients in the supine position only. Image artefact was more frequent in MRE than in MRFT （29.2% vs 18.4%）, but was not statistically significant （P = 0.30）. Adequate distension of the distal SB was obtained in 97.8% of MRFT examinations and in 95.4% of MRE examinations, respectively. Proximal SB distension was, however, less frequently optimal in MRFT than in MRE （P = 0.0036）, particularly in patients over the age of 50 years （P = 0.0099）. Image quality was good in all examinations. CONCLUSION： All patients could be successfully iraaged in the supine position. MRE and MRFT are equivalent for distal SB distension and artefact effects. Proximal SB distension is frequently less optimal in MRFT than in MRE. MRE is, therefore, the preferred MR examination method of the SB.
文摘In order to develop skin artefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone nlbber and knitted nylon sheet were selected to manufacture an artificial skin, due to their higher elastic strain and high flexibility. Tensile and scissors cutting tests were conducted to characterise the matrix and reinforcing materials and the skin artefact. Material properties of the individual and the composite materials were compared with the measured properties of real octopus skin presented ill Part I. The Young＇s modulus of the skin should be below 20 MPa and the elastic strain range should be over 60%. The fracture toughness should be at least 0.9 kJ.m 2. Tubes made of the skin artefact filled with liquid were tested to study volume change under deformation. Finite element analysis model was developed to simulate the material and arm structure under tensile loading. Results show that the skin artefact developed has similar mechanical properties as the real octopus skin and satisfies all the design specifications of the OCTOPUS robot.
文摘In order to fabricate a biomimetic skin for an octopus inspired robot, a new process was developed based on mechanical properties measured from real octopus skin. Various knitted nylon textiles were tested and the one of 10-denier nylon was chosen as reinforcement. A combination of Ecoflex 0030 and 0010 silicone rubbers was used as matrix of the composite to obtain the right stiffness for the skin-analogue system. The open mould fabrication process developed allows air bubble to escape easily and the artificial skin produced was thin and waterproof. Material properties of the biomimetic skin were char- acterised using static tensile and instrumented scissors cutting tests. The Young＇s moduli of the artificial skin are 0.08 MPa and 0.13 MPa in the longitudinal and transverse directions, which are much lower than those of the octopus skin. The strength and fracture toughness of the artificial skin, on the other hand are higher than those of real octopus skins. Conically-shaped skin prototypes to be used to cover the robotic arm unit were manufactured and tested. The biomimetic skin prototype was stiff enough to maintain it conical shape when filled with water. The driving force for elongation was reduced significantly compared with previous prototypes.
文摘Magnetic resonance elastography (MRE) allows the quantitative assessment of the stiffness of tissues based on the tissue response to oscillatory shear stress. Shear wave displacements of the tissues are encoded as phase shifts and converted to stiffness (elastogram). Generally, a partial volume effect occurs when different materials are encompassed on the same voxel. In MRE, however, the partial volume effect occurs even if the voxel is filled with the same materials because wave displacements due to vibrations are spatially distributed. The purpose of this study was to investigate how the partial volume effect can affect the phase shift and the elastogram in MRE. We assumed that the partial volume effect appears only in the slice thickness direction and performed a simulation and MRE experiment with various slice thicknesses (1 - 19 mm), two types of imaging plane (coronal and axial) and two types of vibration frequency (100 and 200 Hz). The results of the simulation and the MRE experiment were similar, and indicated that the phase shift and the elastogram changed variously depending on the slice thickness, the wave pattern and the vibration frequency, even if the voxel was filled with the same material. To reduce the partial volume effect, it is necessary to perform the MRE under the following conditions: Use a wave pattern which barely causes this artefact, a smaller voxel size and a lower vibration frequency.
基金The National Key Research and Development Program of China[grant numbers 2020YFC2004003 and 2020YFC2004002].
文摘The existing UAV aerial image de-fog methods have low image contrast after de-fog,the difference between light and dark image is not obvious,leading to poor de-fog effect.Therefore,an aerial image de-fog enhancement method based on dark channel a priori is proposed.The image variance and absolute gradient mean are combined to get the weight coefficients,and the edge pixels are smoothed by using the multiple decomposition form.The image intensity is calculated and the noise is reduced.A convolution neural network is introduced to calculate the atmospheric transmittance in haze.Based on this,dark channel prior algorithm is used to enhance the light and shade difference of aerial photography image and realise the de-fog enhancement of aerial photography image.To verify the performance of the proposed method,simulation experiments are designed which were compared with the existing methods results in better fog-removing effect,higher contrast and shorter time.
基金the Project of Science and Technology Commission of Shanghai Municipality(No.19411950100)the Multicenter Clinical Research Program of Shanghai Jiao Tong University School of Medicine(No.DLY201822)the Fundamental Research Program Funding of Ninth People’s Hospital affiliated to Shanghai Jiao Tong University School of Medicine(No.JYZZ102)。
文摘The aim of this study was to evaluate the accuracy and reproducibility of a morphological contour interpolation(MCI)based segmentation method for the volumetric measurement of bone grafts around implants.Three 3D-printed models(one with a cylinder and two with a geometrically-complex form)were fabricated to simulate implant placement with a simultaneous guided bone regeneration(GBR)procedure.All models were scanned using a cone beam computed tomography(CBCT)instrument with the same parameters.The true volumes of the bone grafts in the models were assessed using computer-aided calculation(controls).For the test measurements,both manual and MCI-based methods were used.A comparison between the measured and true volumes was performed to evaluate the accuracy.The coefficients of variation of repeated measurements were calculated to evaluate the reproducibility.In addition,the execution time was recorded and a comparison between the two methods was performed.The high accuracy of the MCI-based method was found with differences between the measured value and actual volume,which never exceeded 7.3%.Excellent reproducibility was shown,with coefficients of variation never exceeding 1.1%.A shorter execution time was observed for the MCI-based method than for the manual method.Within the confines of this study,the MCI-based method may be suitable for volumetric measurements of grafted bone around implants.
基金supported by the Ministry of Science and Technology of China (Grant No. 2014FY210500)the National Natural Science Foundation of China (Grant No. 41372187)
文摘The Lop Nur region, in the east part of Tarim Basin, was an important transportation junction between west and east,north and south Eurasia. However, previous studies on prehistoric human activity have concentrated mostly on the Bronze Age,whereas that during the Stone Age remains largely unresearched. Here, we present a new direct evidence of human activity in the late Pleistocene, recorded on a grinding stone buried in a lacustrine sediment section of the Lop Nur region. The grain size distribution of the sediment section indicates that the site was probably in the center of a lake with weak hydrodynamic environment. Therefore, the stone artifact can only be carried to here by people instead of river and it was never move as soon as left here. Results of radiocarbon dating, the evident stratigraphic relations between the stone artifact and the sedimentary formation, indicate that the human activity could extend to approximately 13 ka BP. Furthermore, the results of starch-grain and use-wear analyses suggest that ancient humans gathered seeds of Triticeae, roots, and tubers and used the grinding stone to simply process selected plant as plant foodstuffs during this period. It implies that the environmental conditions in the river delta of the Lop Nur were inhabitable during the late Pleistocene.
