In this paper,the dynamic characteristics of the cylindrical bubbles under triple-frequency acoustic excitation are investigated theoretically.The analytical solution of the primary-superharmonic-subharmonic(PRI-SUPER...In this paper,the dynamic characteristics of the cylindrical bubbles under triple-frequency acoustic excitation are investigated theoretically.The analytical solution of the primary-superharmonic-subharmonic(PRI-SUPER-SUB)simultaneous resonance is obtained through the multi-scale method.Based on the analysis of the frequency response,the influencing mechanisms of the primary parameters(e.g.,the total amplitude,amplitude ratio,liquid viscosity,polytropic exponent,and bubble equilibrium radius)on the resonance are investigated quantitatively.The main conclusions include:(1)The solution for the simultaneous resonance of the cylindrical bubble exhibits jumping and hysteresis phenomena in the vicinity of the resonance frequency.(2)As the total amplitude,amplitude ratio,and equilibrium radius increase,the response amplitude of the PRI-SUPER-SUB simultaneous resonance increases,while the influence of the viscosity is the opposite.(3)The regions dominated by the instability of the simultaneous resonance is significantly affected by the system parameters.展开更多
基于平均法研究了分数阶van der Pol振子3次超谐与1/3次亚谐联合共振时的动力学特性。得到了系统的一阶近似解析解,提出了超、亚谐联合共振时等效线性阻尼和等效线性刚度的概念。建立了联合共振定常解幅频曲线的解析表达式,又结合变分...基于平均法研究了分数阶van der Pol振子3次超谐与1/3次亚谐联合共振时的动力学特性。得到了系统的一阶近似解析解,提出了超、亚谐联合共振时等效线性阻尼和等效线性刚度的概念。建立了联合共振定常解幅频曲线的解析表达式,又结合变分方程进行线性化处理,推导出分数阶van der Pol振子在联合共振时的周期解稳定性判断准则。通过与单一谐波下超谐共振、亚谐共振的对比,发现在不同基本参数下该系统可分别表现出单谐波超谐共振、单谐波亚谐共振以及两者共存时的特征现象。研究表明,分数阶微分项参数通过等效线性阻尼和等效线性刚度的形式对系统的响应幅值、共振频率、定常解稳定性、周期解数量、共振区域、曲线拓扑结构及跳跃现象等复杂动力学特性均产生重要影响。展开更多
The sol–gel method was used to synthesize a series of metal oxides-supported activated carbon fiber (ACF) and the simultaneous catalytic hydrolysis activity of carbonyl sulfide (COS)and carbon disulfide (CS2) at rela...The sol–gel method was used to synthesize a series of metal oxides-supported activated carbon fiber (ACF) and the simultaneous catalytic hydrolysis activity of carbonyl sulfide (COS)and carbon disulfide (CS2) at relatively low temperatures of 60°C was tested.The effects of preparation conditions on the catalyst properties were investigated,including the kinds and amount of metal oxides and calcination temperatures.The activity tests indicated that catalysts with 5 wt.%Ni after calcining at 400°C (Ni(5)/ACF(400)) had the best performance for the simultaneous catalytic hydrolysis of COS and CS2.The surface and structure properties of prepared ACF were characterized by scanning electron microscope-energy disperse spectroscopy (SEM-EDS),Brunauer–Emmett–Teller (BET),X-ray diffraction (XRD),carbon dioxidetemperature programmed desorption (CO2-TPD) and diffuse reflectance Fourier transform infrared reflection (DRFTIR).And the metal cation defects were researched by electron paramagnetic resonance (EPR) method.The characterization results showed that the supporting of Ni on the ACF made the ACF catalyst show alkaline and increased the specific surface area and the number of micropores,then improved catalytic hydrolysis activity.The DRFTIR results revealed that-OH species could facilitate the hydrolysis of COS and CS2;-COO and-C–O species could facilitate the oxidation of catalytic hydrolysate H2S.And the EPR results showed that high calcination temperature conditions provide more active reaction center for the COS and CS2 adsorption.展开更多
In this paper,the simultaneous resonance of a ferromagnetic thin plate in a time-varying magnetic field,having axial speed and being subjected to a periodic line load,is studied.Based on the large deflection theory of...In this paper,the simultaneous resonance of a ferromagnetic thin plate in a time-varying magnetic field,having axial speed and being subjected to a periodic line load,is studied.Based on the large deflection theory of thin plates and electromagnetic field theory,the nonlinear vibration differential equation of the plate is obtained by using the Hamilton′s principle and the Galerkin method.Then the boundary condition in which the longer opposite sides are clamped and hinged is considered.The dimensionless nonlinear differential equations are solved by using the method of multiple scales,and the analytical solution is given.In addition,the stability analysis is also carried out by using Lyapunov stability theory.Through numerical analysis,the variation curves of system resonance amplitude with frequency tuning parameter,magnetic field strength and external excitation amplitude are obtained.Different parameters that have significant effects on the response of the system,such as the thickness,the axial velocity,the magnetic field intensity,the position,and the frequency of external excitation,are considered and analyzed.The results show that the system has multiple solution regions and obvious nonlinear coupled characteristics.展开更多
In the present paper,two-and three-dimensional numerical simulations of the flow interference between four cylinders in an in-line square arrangement at Re = 200 are performed.Assisted with the two-dimensional(2-D) nu...In the present paper,two-and three-dimensional numerical simulations of the flow interference between four cylinders in an in-line square arrangement at Re = 200 are performed.Assisted with the two-dimensional(2-D) numerical simulation,the mean and fluctuating forces,Strouhal number(St) and vortex shedding pattern in the wake for each cylinder were analyzed with the spacing ratio(L /D) ranging from 1.5 to 6.0.It was found that,four different vortex modes(viz.,flip-flopping,shielding anti-phase-synchronized,in-phasesynchronized and anti-phase-synchronized) gradually appear with the increase of the L/D ratio.The average drag coefficient of the upstream cylinders is larger than that of the downstream cylinders,while the downstream cylinders usually undergo serious fluctuating forces.When the L/D ratio ranges from 3.0 to 4.0,the dominant frequency of the drag coefficient is equal to the value of St of upstream cylinders.This indicates that a simultaneous resonance in the in-flow and cross-flow directions may occur for some single structures of a multi-body oscillating system.For the 3-D numerical simulation,the L/D and aspect ratios are kept constant as 5.0 and 10,respectively.It was found that some vortices are formed in the wake of the upstream cylinders.Besides,with the same spacing ratio,the calculated drag coefficient and lift coefficient fluctuation are slightly larger than the 2-D results,but with a phase difference.展开更多
目的探讨三维同步非增强血管造影和斑块内出血(threedimensionalsimultaneous noncontrast angiography and intra plaque hemorrhage,3D-SNAP)高分辨磁共振成像技术对颅内动脉夹层的诊断价值。材料与方法连续收集2015年1月至2018年3月...目的探讨三维同步非增强血管造影和斑块内出血(threedimensionalsimultaneous noncontrast angiography and intra plaque hemorrhage,3D-SNAP)高分辨磁共振成像技术对颅内动脉夹层的诊断价值。材料与方法连续收集2015年1月至2018年3月陕西省人民医院神经内科43例后循环短暂性脑缺血发作(transientischemicattack,TIA)或脑梗死患者,其中颅内动脉夹层18例,非动脉夹层25例,所有患者均采用PhilipsIngenia 3.0 T MRI获取TOF-MRA、T1WI-VISTA、T2WI、3D-SNAP、CE-T1WI成像,双盲分析各序列颅内动脉夹层征象。采用卡方检验、独立样本t检验分析夹层组与非夹层组临床基本资料以及夹层组各序列影像学特征;利用受试者工作特征(receiveroperating characteristic,ROC)曲线比较各序列对颅内动脉夹层的诊断效能。结果 (1)夹层组年龄较非夹层组低,差异有统计学意义(P<0.05),两组间性别、血压、糖尿病、吸烟差异均无统计学意义。(2)6例患者在TOF-MRA、T2WI、T1WI-VISTA、SNAP及CE-T1WI成像序列同时显示夹层瘤样扩张、真假腔、壁内血肿、内膜瓣征象;颅内动脉夹层壁内血肿、双腔征及内膜瓣显示率高分辨MRI各序列比较差异有统计学意义(P<0.05),SNAP显示壁内血肿最敏感,CE-T1WI显示双腔征、内膜瓣征最敏感。(3) TOF-MRA、T2WI、T1WI-VISTA、3D-SNAP、CE-T1WI、SNAP联合CE-T1WI成像序列诊断颅内动脉夹层ROC曲线下面积分别为0.663、0.492、0.729、0.741、0.752、0.824。结论 3D-SNAP高分辨磁共振成像技术无创性、有效评价颅内动脉夹层具有无限的潜力和广阔的前景。展开更多
Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid(HA) to form composite contaminants.As an in...Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid(HA) to form composite contaminants.As an innovative recycled coagulant aid,Enteromorpha polysaccharides(Ep) were associated with polyaluminum chloride(PACl)(denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu2+and HA in this study.The influence of different Al species coagulants(AlCl3, PAClb and PAClc) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail.Results showed that in the three PACl-Ep systems, PAClb-Ep gave the highest removal efficiencies for turbidity and Cu2+, and the best UV254 removal effect was reached by using PAClc-Ep.Higher contents of Alb and Alc contributed to great coagulation performance because of their stronger bridging and sweeping effects.For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions.Additionally, smaller and more agminated flocs with great recovery ability were formed by PAClb-Ep and PAClc-Ep systems(bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species).Similarly,due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.展开更多
BACKGROUND Chronic cocaine use is associated with stroke, coronary artery disease and myocardial infarction, resulting in severe impairments or sudden mortality. In the absence of clear cardiovascular symptoms, indivi...BACKGROUND Chronic cocaine use is associated with stroke, coronary artery disease and myocardial infarction, resulting in severe impairments or sudden mortality. In the absence of clear cardiovascular symptoms, individuals with cocaine use disorder (iCUD) seeking addiction treatment receive mostly psychotherapy and psychiatric pharmacotherapy, with no attention to vascular disease (i.e., atherosclerosis). Little is known about the pre-clinical signs of cardiovascular risk in iCUD and early signs of vascular disease are undetected in this underserved population. AIM To assess inflammation, plaque burden and plaque composition in iCUD aiming to detect markers of atherosclerosis and vascular disease. METHODS The bilateral carotid arteries were imaged with positron emission tomography/magnetic resonance imaging (PET/MRI) in iCUD asymptomatic for cardiovascular disease, healthy controls, and individuals with cardiovascular risk. PET with 18F-fluorodeoxyglucose (18F-FDG) evaluated vascular inflammation and 3-D dark-blood MRI assessed plaque burden including wall area and thickness. Drug use and severity of addiction were assessed with standardized instruments. RESULTS The majority of iCUD and controls had carotid FDG-PET signal greater than 1.6 but lower than 3, indicating the presence of mild to moderate inflammation. However, the MRI measure of wall structure was thicker in iCUD as compared to the controls and cardiovascular risk group, indicating greater carotid plaque burden. iCUD had larger wall area as compared to the healthy controls but not as compared to the cardiovascular risk group, indicating structural wall similarities between the non-control study groups. In iCUD, wall area correlated with greater cocaine withdrawal and craving. CONCLUSION These preliminary results show markers of carotid artery disease burden in cardiovascular disease-asymptomatic iCUD. Broader trials are warranted to develop protocols for early detection of cardiovascular risk and preventive intervention in iCUD.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51976056).
文摘In this paper,the dynamic characteristics of the cylindrical bubbles under triple-frequency acoustic excitation are investigated theoretically.The analytical solution of the primary-superharmonic-subharmonic(PRI-SUPER-SUB)simultaneous resonance is obtained through the multi-scale method.Based on the analysis of the frequency response,the influencing mechanisms of the primary parameters(e.g.,the total amplitude,amplitude ratio,liquid viscosity,polytropic exponent,and bubble equilibrium radius)on the resonance are investigated quantitatively.The main conclusions include:(1)The solution for the simultaneous resonance of the cylindrical bubble exhibits jumping and hysteresis phenomena in the vicinity of the resonance frequency.(2)As the total amplitude,amplitude ratio,and equilibrium radius increase,the response amplitude of the PRI-SUPER-SUB simultaneous resonance increases,while the influence of the viscosity is the opposite.(3)The regions dominated by the instability of the simultaneous resonance is significantly affected by the system parameters.
文摘基于平均法研究了分数阶van der Pol振子3次超谐与1/3次亚谐联合共振时的动力学特性。得到了系统的一阶近似解析解,提出了超、亚谐联合共振时等效线性阻尼和等效线性刚度的概念。建立了联合共振定常解幅频曲线的解析表达式,又结合变分方程进行线性化处理,推导出分数阶van der Pol振子在联合共振时的周期解稳定性判断准则。通过与单一谐波下超谐共振、亚谐共振的对比,发现在不同基本参数下该系统可分别表现出单谐波超谐共振、单谐波亚谐共振以及两者共存时的特征现象。研究表明,分数阶微分项参数通过等效线性阻尼和等效线性刚度的形式对系统的响应幅值、共振频率、定常解稳定性、周期解数量、共振区域、曲线拓扑结构及跳跃现象等复杂动力学特性均产生重要影响。
基金supported by the National Key R&D Program of China (No.2018YFC0213400)the National Natural Science Foundation of China (Nos.51968034,41807373,21667015 and51708266)the Science and Technology Program of Yunnan province (No.2019FB069)。
文摘The sol–gel method was used to synthesize a series of metal oxides-supported activated carbon fiber (ACF) and the simultaneous catalytic hydrolysis activity of carbonyl sulfide (COS)and carbon disulfide (CS2) at relatively low temperatures of 60°C was tested.The effects of preparation conditions on the catalyst properties were investigated,including the kinds and amount of metal oxides and calcination temperatures.The activity tests indicated that catalysts with 5 wt.%Ni after calcining at 400°C (Ni(5)/ACF(400)) had the best performance for the simultaneous catalytic hydrolysis of COS and CS2.The surface and structure properties of prepared ACF were characterized by scanning electron microscope-energy disperse spectroscopy (SEM-EDS),Brunauer–Emmett–Teller (BET),X-ray diffraction (XRD),carbon dioxidetemperature programmed desorption (CO2-TPD) and diffuse reflectance Fourier transform infrared reflection (DRFTIR).And the metal cation defects were researched by electron paramagnetic resonance (EPR) method.The characterization results showed that the supporting of Ni on the ACF made the ACF catalyst show alkaline and increased the specific surface area and the number of micropores,then improved catalytic hydrolysis activity.The DRFTIR results revealed that-OH species could facilitate the hydrolysis of COS and CS2;-COO and-C–O species could facilitate the oxidation of catalytic hydrolysate H2S.And the EPR results showed that high calcination temperature conditions provide more active reaction center for the COS and CS2 adsorption.
基金National Natural Science Foundation of China under Grant Nos.12172321 and 11472239Hebei Provincial Natural Science Foundation of China under Grant No.A2020203007Hebei Provincial Graduate Innovation Foundation of China under Grant No.CXZZBS2022146。
文摘In this paper,the simultaneous resonance of a ferromagnetic thin plate in a time-varying magnetic field,having axial speed and being subjected to a periodic line load,is studied.Based on the large deflection theory of thin plates and electromagnetic field theory,the nonlinear vibration differential equation of the plate is obtained by using the Hamilton′s principle and the Galerkin method.Then the boundary condition in which the longer opposite sides are clamped and hinged is considered.The dimensionless nonlinear differential equations are solved by using the method of multiple scales,and the analytical solution is given.In addition,the stability analysis is also carried out by using Lyapunov stability theory.Through numerical analysis,the variation curves of system resonance amplitude with frequency tuning parameter,magnetic field strength and external excitation amplitude are obtained.Different parameters that have significant effects on the response of the system,such as the thickness,the axial velocity,the magnetic field intensity,the position,and the frequency of external excitation,are considered and analyzed.The results show that the system has multiple solution regions and obvious nonlinear coupled characteristics.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50538020)
文摘In the present paper,two-and three-dimensional numerical simulations of the flow interference between four cylinders in an in-line square arrangement at Re = 200 are performed.Assisted with the two-dimensional(2-D) numerical simulation,the mean and fluctuating forces,Strouhal number(St) and vortex shedding pattern in the wake for each cylinder were analyzed with the spacing ratio(L /D) ranging from 1.5 to 6.0.It was found that,four different vortex modes(viz.,flip-flopping,shielding anti-phase-synchronized,in-phasesynchronized and anti-phase-synchronized) gradually appear with the increase of the L/D ratio.The average drag coefficient of the upstream cylinders is larger than that of the downstream cylinders,while the downstream cylinders usually undergo serious fluctuating forces.When the L/D ratio ranges from 3.0 to 4.0,the dominant frequency of the drag coefficient is equal to the value of St of upstream cylinders.This indicates that a simultaneous resonance in the in-flow and cross-flow directions may occur for some single structures of a multi-body oscillating system.For the 3-D numerical simulation,the L/D and aspect ratios are kept constant as 5.0 and 10,respectively.It was found that some vortices are formed in the wake of the upstream cylinders.Besides,with the same spacing ratio,the calculated drag coefficient and lift coefficient fluctuation are slightly larger than the 2-D results,but with a phase difference.
文摘目的探讨三维同步非增强血管造影和斑块内出血(threedimensionalsimultaneous noncontrast angiography and intra plaque hemorrhage,3D-SNAP)高分辨磁共振成像技术对颅内动脉夹层的诊断价值。材料与方法连续收集2015年1月至2018年3月陕西省人民医院神经内科43例后循环短暂性脑缺血发作(transientischemicattack,TIA)或脑梗死患者,其中颅内动脉夹层18例,非动脉夹层25例,所有患者均采用PhilipsIngenia 3.0 T MRI获取TOF-MRA、T1WI-VISTA、T2WI、3D-SNAP、CE-T1WI成像,双盲分析各序列颅内动脉夹层征象。采用卡方检验、独立样本t检验分析夹层组与非夹层组临床基本资料以及夹层组各序列影像学特征;利用受试者工作特征(receiveroperating characteristic,ROC)曲线比较各序列对颅内动脉夹层的诊断效能。结果 (1)夹层组年龄较非夹层组低,差异有统计学意义(P<0.05),两组间性别、血压、糖尿病、吸烟差异均无统计学意义。(2)6例患者在TOF-MRA、T2WI、T1WI-VISTA、SNAP及CE-T1WI成像序列同时显示夹层瘤样扩张、真假腔、壁内血肿、内膜瓣征象;颅内动脉夹层壁内血肿、双腔征及内膜瓣显示率高分辨MRI各序列比较差异有统计学意义(P<0.05),SNAP显示壁内血肿最敏感,CE-T1WI显示双腔征、内膜瓣征最敏感。(3) TOF-MRA、T2WI、T1WI-VISTA、3D-SNAP、CE-T1WI、SNAP联合CE-T1WI成像序列诊断颅内动脉夹层ROC曲线下面积分别为0.663、0.492、0.729、0.741、0.752、0.824。结论 3D-SNAP高分辨磁共振成像技术无创性、有效评价颅内动脉夹层具有无限的潜力和广阔的前景。
基金supported by the Taishan Scholar Program (No.ts 201511003)the National Natural Science Foundation of China (No.51478250).
文摘Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid(HA) to form composite contaminants.As an innovative recycled coagulant aid,Enteromorpha polysaccharides(Ep) were associated with polyaluminum chloride(PACl)(denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu2+and HA in this study.The influence of different Al species coagulants(AlCl3, PAClb and PAClc) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail.Results showed that in the three PACl-Ep systems, PAClb-Ep gave the highest removal efficiencies for turbidity and Cu2+, and the best UV254 removal effect was reached by using PAClc-Ep.Higher contents of Alb and Alc contributed to great coagulation performance because of their stronger bridging and sweeping effects.For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions.Additionally, smaller and more agminated flocs with great recovery ability were formed by PAClb-Ep and PAClc-Ep systems(bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species).Similarly,due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.
基金Supported by NIDA,No.K23DA045928-01(to Bachi K) and No.R01DA041528(to Goldstein RZ)NIH/NHLBI,No.R01HL071021+1 种基金Translational and Molecular Imaging Institute internal funding(to Fayad ZAF)American Heart Association Grant in Aid,No.17GRNT33420119(to Mani VM)
文摘BACKGROUND Chronic cocaine use is associated with stroke, coronary artery disease and myocardial infarction, resulting in severe impairments or sudden mortality. In the absence of clear cardiovascular symptoms, individuals with cocaine use disorder (iCUD) seeking addiction treatment receive mostly psychotherapy and psychiatric pharmacotherapy, with no attention to vascular disease (i.e., atherosclerosis). Little is known about the pre-clinical signs of cardiovascular risk in iCUD and early signs of vascular disease are undetected in this underserved population. AIM To assess inflammation, plaque burden and plaque composition in iCUD aiming to detect markers of atherosclerosis and vascular disease. METHODS The bilateral carotid arteries were imaged with positron emission tomography/magnetic resonance imaging (PET/MRI) in iCUD asymptomatic for cardiovascular disease, healthy controls, and individuals with cardiovascular risk. PET with 18F-fluorodeoxyglucose (18F-FDG) evaluated vascular inflammation and 3-D dark-blood MRI assessed plaque burden including wall area and thickness. Drug use and severity of addiction were assessed with standardized instruments. RESULTS The majority of iCUD and controls had carotid FDG-PET signal greater than 1.6 but lower than 3, indicating the presence of mild to moderate inflammation. However, the MRI measure of wall structure was thicker in iCUD as compared to the controls and cardiovascular risk group, indicating greater carotid plaque burden. iCUD had larger wall area as compared to the healthy controls but not as compared to the cardiovascular risk group, indicating structural wall similarities between the non-control study groups. In iCUD, wall area correlated with greater cocaine withdrawal and craving. CONCLUSION These preliminary results show markers of carotid artery disease burden in cardiovascular disease-asymptomatic iCUD. Broader trials are warranted to develop protocols for early detection of cardiovascular risk and preventive intervention in iCUD.
