The fish cage design requires accurate predictions of long-term extreme loads and responses.Compared with the time-consuming full long-term analysis method integrating all the probability distribution of the short-ter...The fish cage design requires accurate predictions of long-term extreme loads and responses.Compared with the time-consuming full long-term analysis method integrating all the probability distribution of the short-term extremes,the environmental contour method gains much attention in predicting the long-term extreme values due to the less computational effort.This paper investigates the long-term extreme response of a fish cage using the environmental contour method.The fish cage is numerically simulated based on the lumped-mass method and the curved beam theory.Based on the one-dimensional(1D)and two-dimensional(2D)environmental contour,the extreme responses,including the surge and heave motions,mooring force,and vertical bending of the floater,are predicted for different return periods and compared with the full long-term analysis results.Results indicate that the 1D method greatly underestimates the extreme values.The 2D environmental contour method with a higher percentile level,namely90%,provides reasonable estimations and seems to be suitable for the long-term value analysis.Sensitivity studies show that the mooring arrangement and the bending stiffness have great effects on the bending moment and the mooring force and the mooring line pre-tension has minor effects on the fish cage response.展开更多
研究提出一种通过化学键键能差进行能量密度快速估算的方法,和一种利用拉普拉斯键级和分子片段键离解能相结合快速判断笼型结构稳定性的方法。通过穷举法构建了基于Noradamantane的所有富氮骨架及其435种硝基衍生物,应用上述计算方法筛...研究提出一种通过化学键键能差进行能量密度快速估算的方法,和一种利用拉普拉斯键级和分子片段键离解能相结合快速判断笼型结构稳定性的方法。通过穷举法构建了基于Noradamantane的所有富氮骨架及其435种硝基衍生物,应用上述计算方法筛选兼具高能量密度和稳定性的分子结构,并采用量子化学能量计算和过渡态反应势垒计算验证筛选结果的可靠性。计算发现了两种兼顾高能量密度和结构稳定性的硝基化合物,其爆热、爆速、爆压和金属加速能力的理论计算最大值分别达到7.77 k J·g^(-1)、10.1 km·s^(-1)、47 GPa和1.14倍HMX的金属加速能力,且结构分解反应势垒≥96 k J·mol^(-1)。本研究所建立的含能分子能量密度和稳定性快速筛选方法,可为高能稳定的含能分子设计提供参考。展开更多
目的评估基于磁共振成像(MRI)的腰肌质量参数对腰椎后路椎间融合术(PLIF)后融合器下沉的预测价值。方法对2019年2月至2023年2月接受单节段PLIF的165例病人进行回顾性研究,男75例,女90例,年龄为(65.02±8.55)岁。随访12个月以上,45例...目的评估基于磁共振成像(MRI)的腰肌质量参数对腰椎后路椎间融合术(PLIF)后融合器下沉的预测价值。方法对2019年2月至2023年2月接受单节段PLIF的165例病人进行回顾性研究,男75例,女90例,年龄为(65.02±8.55)岁。随访12个月以上,45例(27.3%)发生融合器沉降,根据是否发生术后融合器沉降分为沉降组(45例)与非沉降组(120例)。术前在MRI上测量腰肌指数(PMI)和腰肌质量评分(Goutallier分级),以及椎体骨质量(vertebral bone quality,VBQ)、终板骨质量(endplate bone quality,EBQ);基于CT,测量计算机断层扫描(QCT)骨密度值。比较两组病人的年龄、性别、身体质量指数(BMI)、手术节段、PMI、Goutallier分级等;采用Logistic回归分析融合器下沉的影响因素;PMI、Goutallier分级分别与融合器沉降高度、QCT骨密度值进行相关性分析;比较不同手术节段中的PMI、Goutallier分级;绘制受试者工作特征曲线(ROC),计算各预测因子的曲线下面积(AUC)。结果沉降组与非沉降组的年龄、性别、BMI、Goutallier分级、PMI、VBQ、EBQ比较,差异有统计学意义(P<0.05)。Logistic回归分析结果显示年龄、性别、QCT骨密度值、VBQ、PMI、Goutallier分级是融合器沉降的影响因素。相关性分析结果显示PMI与融合器沉降高度呈显著负相关(r=-0.402,P<0.05),与QCT骨密度值呈显著正相关(r=3.390,P<0.05);Goutallier分级与融合器沉降高度呈正相关(r=0.289,P<0.05),与QCT骨密度值呈负相关(r=-0.286,P<0.05),与PMI呈负相关(r=-0.462,P<0.05)。PMI的AUC为0.826(95%CI:0.756,0.896),最佳沉降边界为6.94 cm^(2)/m^(2),Goutallier分级的AUC为0.786(95%CI:0.719,0.854),最佳沉降边界1.5级。结论PMI和Goutallier分级可能是PLIF术后融合器沉降的重要预测指标。展开更多
A numerical model for determining fishing net configuration and load is developed, based on the lumped masses method. The model is used to analyze the influences on the net of gravity sea cage by different sinker weig...A numerical model for determining fishing net configuration and load is developed, based on the lumped masses method. The model is used to analyze the influences on the net of gravity sea cage by different sinker weights in uniform flow. The net of gravity sea cage is simulated under different current velocities and sinker weights. In order to verify the validity of the numerical results, model test results made by Lader and Enerhaug are cited and compared with the numerical ones. The results of numerical simulation agree well with the experimental ones and the agreement is within an error range of 13% under different velocities and sinker weights. The numerical results indicate that increasing the sinker weight can effectively reduce the net deformation, but the total drag force on the net will increase accordingly. Results will give references for better knowledge of the hydrodynamic behavior of gravity sea cage.展开更多
This paper aims at investigation of the dynamic properties of gravity cage exposed to waves by use of a numerical model. The numerical model is developed, based on lumped mass method to set up the equations of motion ...This paper aims at investigation of the dynamic properties of gravity cage exposed to waves by use of a numerical model. The numerical model is developed, based on lumped mass method to set up the equations of motion of the whole cage; meanwhile the solutions of equations are solved by the Runge-Kutta-Vemer fifth-order and sixth-order method. Physical model tests have been carried out to examine the validity of the numerical model. The results by the numerical simulation agree well with the experimental data.展开更多
A dynamics formula was established for the flexible cage of high-speed angular contact ball bearing. A modified Craig-Bampton component mode synthetic method was used to establish the formula with regard to the flexib...A dynamics formula was established for the flexible cage of high-speed angular contact ball bearing. A modified Craig-Bampton component mode synthetic method was used to establish the formula with regard to the flexibility of cage and based on a dynamic analysis of angular contact ball bearing,and a rigid-flexible multi-body dynamic analysis program was developed using ADAMS,which is verified by a computation example of Gupta. The results show that it's not likely to keep the rotation smoothness of cage when the ratio of pocket clearance to guiding clearance and the ratio of radial load to axial load become too large or too small. By comparison,the flexible cage runs more smoothly than the rigid cage.展开更多
Backgrou nd Dense titanium(Ti)fusion cages have been commonly used in transforaminal lumbar interbody fusion.However,the stiffness mismatch between cages and adjacent bone endplates increases the risk of stress shield...Backgrou nd Dense titanium(Ti)fusion cages have been commonly used in transforaminal lumbar interbody fusion.However,the stiffness mismatch between cages and adjacent bone endplates increases the risk of stress shielding and cage subsidence.Methods The current study presents a multiscale optimization approach for porous Ti fusion cage development,including microscale topology optimization based on homogenization theory that obtains a unit cell with prescribed mechanical properties,and macroscale topology optimization that determines the layout of framework structure over the porous cage while maintaining the desired stiffness.The biomechanical performance of the designed porous cage is assessed using numerical simulations of fusion surgery.Selective laser melting is employed to assists with fabricating the designed porous structure and porous cage.Results The simulations demonstrate that the designed porous cage increases the strain energy density of bone grafts and decreases the peak stress on bone endplates.The mechanical and morphological discrepancies between the as-designed and fabricated porous structures are also described.Conclusion From the perspective of biomechanics,it is demonstrated that the designed porous cage contributes to reducing the risk of stress shielding and cage subsidence.The optimization of processing parameters and post-treatments are required to fabricate the designed porous cage.The present multiscale optimization approach can be extended to the development of cages with other shapes or materials and further types of orthopedic implants.展开更多
基金financially supported by the China Postdoctoral Science Foundation(Grant No.2019M661024]the Open Foundation of State Key Laboratory of Coastal and Offshore Engineering(Grant No.LP1901)。
文摘The fish cage design requires accurate predictions of long-term extreme loads and responses.Compared with the time-consuming full long-term analysis method integrating all the probability distribution of the short-term extremes,the environmental contour method gains much attention in predicting the long-term extreme values due to the less computational effort.This paper investigates the long-term extreme response of a fish cage using the environmental contour method.The fish cage is numerically simulated based on the lumped-mass method and the curved beam theory.Based on the one-dimensional(1D)and two-dimensional(2D)environmental contour,the extreme responses,including the surge and heave motions,mooring force,and vertical bending of the floater,are predicted for different return periods and compared with the full long-term analysis results.Results indicate that the 1D method greatly underestimates the extreme values.The 2D environmental contour method with a higher percentile level,namely90%,provides reasonable estimations and seems to be suitable for the long-term value analysis.Sensitivity studies show that the mooring arrangement and the bending stiffness have great effects on the bending moment and the mooring force and the mooring line pre-tension has minor effects on the fish cage response.
文摘研究提出一种通过化学键键能差进行能量密度快速估算的方法,和一种利用拉普拉斯键级和分子片段键离解能相结合快速判断笼型结构稳定性的方法。通过穷举法构建了基于Noradamantane的所有富氮骨架及其435种硝基衍生物,应用上述计算方法筛选兼具高能量密度和稳定性的分子结构,并采用量子化学能量计算和过渡态反应势垒计算验证筛选结果的可靠性。计算发现了两种兼顾高能量密度和结构稳定性的硝基化合物,其爆热、爆速、爆压和金属加速能力的理论计算最大值分别达到7.77 k J·g^(-1)、10.1 km·s^(-1)、47 GPa和1.14倍HMX的金属加速能力,且结构分解反应势垒≥96 k J·mol^(-1)。本研究所建立的含能分子能量密度和稳定性快速筛选方法,可为高能稳定的含能分子设计提供参考。
文摘目的评估基于磁共振成像(MRI)的腰肌质量参数对腰椎后路椎间融合术(PLIF)后融合器下沉的预测价值。方法对2019年2月至2023年2月接受单节段PLIF的165例病人进行回顾性研究,男75例,女90例,年龄为(65.02±8.55)岁。随访12个月以上,45例(27.3%)发生融合器沉降,根据是否发生术后融合器沉降分为沉降组(45例)与非沉降组(120例)。术前在MRI上测量腰肌指数(PMI)和腰肌质量评分(Goutallier分级),以及椎体骨质量(vertebral bone quality,VBQ)、终板骨质量(endplate bone quality,EBQ);基于CT,测量计算机断层扫描(QCT)骨密度值。比较两组病人的年龄、性别、身体质量指数(BMI)、手术节段、PMI、Goutallier分级等;采用Logistic回归分析融合器下沉的影响因素;PMI、Goutallier分级分别与融合器沉降高度、QCT骨密度值进行相关性分析;比较不同手术节段中的PMI、Goutallier分级;绘制受试者工作特征曲线(ROC),计算各预测因子的曲线下面积(AUC)。结果沉降组与非沉降组的年龄、性别、BMI、Goutallier分级、PMI、VBQ、EBQ比较,差异有统计学意义(P<0.05)。Logistic回归分析结果显示年龄、性别、QCT骨密度值、VBQ、PMI、Goutallier分级是融合器沉降的影响因素。相关性分析结果显示PMI与融合器沉降高度呈显著负相关(r=-0.402,P<0.05),与QCT骨密度值呈显著正相关(r=3.390,P<0.05);Goutallier分级与融合器沉降高度呈正相关(r=0.289,P<0.05),与QCT骨密度值呈负相关(r=-0.286,P<0.05),与PMI呈负相关(r=-0.462,P<0.05)。PMI的AUC为0.826(95%CI:0.756,0.896),最佳沉降边界为6.94 cm^(2)/m^(2),Goutallier分级的AUC为0.786(95%CI:0.719,0.854),最佳沉降边界1.5级。结论PMI和Goutallier分级可能是PLIF术后融合器沉降的重要预测指标。
基金This study was financially supported by the National Natural Science Foundation of China under contract No. 50279002the National ＂863＂ High Technology Project of China under contract Nos 2001AA623010 and 2003AA623010the Program for Changjiang Scholars and Innovative Research Team in University of China under contract No. IRT0420.
文摘A numerical model for determining fishing net configuration and load is developed, based on the lumped masses method. The model is used to analyze the influences on the net of gravity sea cage by different sinker weights in uniform flow. The net of gravity sea cage is simulated under different current velocities and sinker weights. In order to verify the validity of the numerical results, model test results made by Lader and Enerhaug are cited and compared with the numerical ones. The results of numerical simulation agree well with the experimental ones and the agreement is within an error range of 13% under different velocities and sinker weights. The numerical results indicate that increasing the sinker weight can effectively reduce the net deformation, but the total drag force on the net will increase accordingly. Results will give references for better knowledge of the hydrodynamic behavior of gravity sea cage.
基金This paper is supported by the National 863 High Technology Development Plan Project (Grant No2006AA100301)the Programfor Changjiang Scholars and Innovative Research Teamin University (IRT-0420)
文摘This paper aims at investigation of the dynamic properties of gravity cage exposed to waves by use of a numerical model. The numerical model is developed, based on lumped mass method to set up the equations of motion of the whole cage; meanwhile the solutions of equations are solved by the Runge-Kutta-Vemer fifth-order and sixth-order method. Physical model tests have been carried out to examine the validity of the numerical model. The results by the numerical simulation agree well with the experimental data.
文摘A dynamics formula was established for the flexible cage of high-speed angular contact ball bearing. A modified Craig-Bampton component mode synthetic method was used to establish the formula with regard to the flexibility of cage and based on a dynamic analysis of angular contact ball bearing,and a rigid-flexible multi-body dynamic analysis program was developed using ADAMS,which is verified by a computation example of Gupta. The results show that it's not likely to keep the rotation smoothness of cage when the ratio of pocket clearance to guiding clearance and the ratio of radial load to axial load become too large or too small. By comparison,the flexible cage runs more smoothly than the rigid cage.
基金financially supported by the National Natural Science Foundation of China(No.51975336)the Key Basic Research Project of Natural Science Foundation of Shandong Province,China(No.ZR2018ZB0106)the Key Research and Development Program of Shandong Province,China(No.2019JZZY010112)。
文摘Backgrou nd Dense titanium(Ti)fusion cages have been commonly used in transforaminal lumbar interbody fusion.However,the stiffness mismatch between cages and adjacent bone endplates increases the risk of stress shielding and cage subsidence.Methods The current study presents a multiscale optimization approach for porous Ti fusion cage development,including microscale topology optimization based on homogenization theory that obtains a unit cell with prescribed mechanical properties,and macroscale topology optimization that determines the layout of framework structure over the porous cage while maintaining the desired stiffness.The biomechanical performance of the designed porous cage is assessed using numerical simulations of fusion surgery.Selective laser melting is employed to assists with fabricating the designed porous structure and porous cage.Results The simulations demonstrate that the designed porous cage increases the strain energy density of bone grafts and decreases the peak stress on bone endplates.The mechanical and morphological discrepancies between the as-designed and fabricated porous structures are also described.Conclusion From the perspective of biomechanics,it is demonstrated that the designed porous cage contributes to reducing the risk of stress shielding and cage subsidence.The optimization of processing parameters and post-treatments are required to fabricate the designed porous cage.The present multiscale optimization approach can be extended to the development of cages with other shapes or materials and further types of orthopedic implants.
