This study presents a significant advancement in the vibration analysis of functionally graded sandwich plates with auxetic cores by introducing a general viscoelastic foundation model that more accurately reflects th...This study presents a significant advancement in the vibration analysis of functionally graded sandwich plates with auxetic cores by introducing a general viscoelastic foundation model that more accurately reflects the complex interactions between the plate and the foundation.The novelty of this study is that the proposed viscoelastic foundation model incorporates elastic and damping effects in both the Winkler and Pasternak layers.To develop the theoretical framework for this analysis,the higher-order shear deformation theory is employed,while Hamilton's principle is used to derive the governing equations of motion.The closed-form solution is used to determine the damped vibration behaviors of the sandwich plates.The precision and robustness of the proposed mathematical model are validated through several comparison studies with existing numerical results.A detailed parametric study is conducted to investigate the influence of various parameters,including the elastic and damping coefficients of the foundation,the material gradation,and the properties of the auxetic core on the vibration behavior of the plates.The numerical results provide new insights into the vibration characteristics of sandwich plates with auxetic cores resting on viscoelastic foundation,highlighting the significant role of the two damping coefficients and auxetic cores in the visco-vibration behavior of the plates.展开更多
首先分析Chirp函数在频域上的一般特性,并且分析Altrea公司提供的数控振荡器知识产权核(NCO IP core)的输入/输出特性,通过MegaCore环境确定其输入控制字,通过外围逻辑电路实时向NCO IP core调入控制频率控制字以达到改变输出频率的目的...首先分析Chirp函数在频域上的一般特性,并且分析Altrea公司提供的数控振荡器知识产权核(NCO IP core)的输入/输出特性,通过MegaCore环境确定其输入控制字,通过外围逻辑电路实时向NCO IP core调入控制频率控制字以达到改变输出频率的目的,并通过在示波器上观测FPGA的运行情况,验证了该设计具有很好的输出效果。展开更多
Whipple shields as sacrificial bumpers,safeguard the satellites against extremely fast,different-sized projectiles traveling through space in the low earth orbit.Typical Whipple shields comprise a front and rear plate...Whipple shields as sacrificial bumpers,safeguard the satellites against extremely fast,different-sized projectiles traveling through space in the low earth orbit.Typical Whipple shields comprise a front and rear plate,separated by a gap or space.Recent advancements have explored the use of foam,cellular cores,and alternative materials such as ceramics instead of aluminium for the plates.In the current work,the effect of including fluid cores(air/water)sandwiched between the front and rear plates,on the response to hypervelocity impact was explored through a numerical approach.The numerical simulation consisted of hypervelocity impact by a 2 mm diameter,stainless steel projectile,launched at speeds of 3 e9 km/s with a normal impact trajectory towards the Whipple shield.The front and rear bumpers,made of AA6061-T6,were each 1 mm thick.A space of 10 mm was taken between the plates(occupied by fluid).The key metrics analyzed were the perforation characteristics,stages of the debris cloud generation and propagation,energy variations(internal,kinetic and plastic work),temperature variations,and the fragmentation summary.From the computational analysis,employing water-core in Whipple shields could prevent the rear bumper perforation till 6 km/s,lower the peak temperatures at the front bumper perforation zones and debris tip,and generate fewer,larger fragments.展开更多
AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal t...AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal that the prepared core-shell nanoparticles were covered by Co shell and exhibited the similar electrochemistry property with the Co nanoparticles surface. Surface enhanced Raman spectroscopy（SERS） activities of these nanoparticles were studied by using pyridine as a probe molecule. It was found that the SERS intensity depended on the Co shell thickness of the core-shell nanoparticles and was weakened with the increasing shell thickness. The SERS intensity of these AucoreCoshell nanoparticles is found to be about twenty times higher than that obtained on an electrochemically roughened cobalt electrode.展开更多
儿童与成人慢性乙型肝炎患者的临床特征差异明显。乙型肝炎病毒(Hepatitis B virus,HBV)病毒准种特征与其致病特性紧密相连,HBV病毒Core基因区富含免疫表位,该区域的准种特征直接反映病毒变异与病毒应对宿主免疫压力间的动态过程。文章...儿童与成人慢性乙型肝炎患者的临床特征差异明显。乙型肝炎病毒(Hepatitis B virus,HBV)病毒准种特征与其致病特性紧密相连,HBV病毒Core基因区富含免疫表位,该区域的准种特征直接反映病毒变异与病毒应对宿主免疫压力间的动态过程。文章通过扩增170名儿童慢性乙型肝炎患者及121名成人慢性乙型肝炎患者病毒Core基因区,按照病毒基因型以及病毒e抗原(Hepatitis B virus e antigen,HBe Ag)状态进行分组,使用序列复杂度、多样性、非同义突变率(Non-synonymous substitution ratio,d N)、同义突变率(Synonymous substitution ratios,d S)等指标衡量不同组别之间的病毒准种特征;使用不同模型计算不同组别中受到正选择压力的位点,进一步结合HBV Core基因区免疫表位信息,进行正选择位点的定位分析。结果发现,儿童乙型肝炎病毒患者体内病毒Core基因区序列复杂性和多样性低于成人患者,且前者Core基因区正选择位点个数显著低于后者,这说明儿童慢性乙型肝炎患者体内病毒受到的选择压力低于成人患者。在儿童及成人慢性感染病人组中,HBe Ag阳性病人体内病毒受到的选择压力低于HBe Ag阴性病人。儿童及成人慢性感染患者体内病毒存在13个正选择位点,大多数正选择位点位于已知的抗原表位上。本研究从分子进化角度揭示了儿童与成人慢性乙型肝炎病例体内病毒Core基因区序列准种差异,为两类病人显著不同的临床表征提供了群体遗传学的解释。展开更多
基金the funding of the Deanship of Graduate Studies and Scientific Research,Jazan University,Saudi Arabia,through project number:RG24-M027.
文摘This study presents a significant advancement in the vibration analysis of functionally graded sandwich plates with auxetic cores by introducing a general viscoelastic foundation model that more accurately reflects the complex interactions between the plate and the foundation.The novelty of this study is that the proposed viscoelastic foundation model incorporates elastic and damping effects in both the Winkler and Pasternak layers.To develop the theoretical framework for this analysis,the higher-order shear deformation theory is employed,while Hamilton's principle is used to derive the governing equations of motion.The closed-form solution is used to determine the damped vibration behaviors of the sandwich plates.The precision and robustness of the proposed mathematical model are validated through several comparison studies with existing numerical results.A detailed parametric study is conducted to investigate the influence of various parameters,including the elastic and damping coefficients of the foundation,the material gradation,and the properties of the auxetic core on the vibration behavior of the plates.The numerical results provide new insights into the vibration characteristics of sandwich plates with auxetic cores resting on viscoelastic foundation,highlighting the significant role of the two damping coefficients and auxetic cores in the visco-vibration behavior of the plates.
文摘首先分析Chirp函数在频域上的一般特性,并且分析Altrea公司提供的数控振荡器知识产权核(NCO IP core)的输入/输出特性,通过MegaCore环境确定其输入控制字,通过外围逻辑电路实时向NCO IP core调入控制频率控制字以达到改变输出频率的目的,并通过在示波器上观测FPGA的运行情况,验证了该设计具有很好的输出效果。
文摘Whipple shields as sacrificial bumpers,safeguard the satellites against extremely fast,different-sized projectiles traveling through space in the low earth orbit.Typical Whipple shields comprise a front and rear plate,separated by a gap or space.Recent advancements have explored the use of foam,cellular cores,and alternative materials such as ceramics instead of aluminium for the plates.In the current work,the effect of including fluid cores(air/water)sandwiched between the front and rear plates,on the response to hypervelocity impact was explored through a numerical approach.The numerical simulation consisted of hypervelocity impact by a 2 mm diameter,stainless steel projectile,launched at speeds of 3 e9 km/s with a normal impact trajectory towards the Whipple shield.The front and rear bumpers,made of AA6061-T6,were each 1 mm thick.A space of 10 mm was taken between the plates(occupied by fluid).The key metrics analyzed were the perforation characteristics,stages of the debris cloud generation and propagation,energy variations(internal,kinetic and plastic work),temperature variations,and the fragmentation summary.From the computational analysis,employing water-core in Whipple shields could prevent the rear bumper perforation till 6 km/s,lower the peak temperatures at the front bumper perforation zones and debris tip,and generate fewer,larger fragments.
文摘AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal that the prepared core-shell nanoparticles were covered by Co shell and exhibited the similar electrochemistry property with the Co nanoparticles surface. Surface enhanced Raman spectroscopy（SERS） activities of these nanoparticles were studied by using pyridine as a probe molecule. It was found that the SERS intensity depended on the Co shell thickness of the core-shell nanoparticles and was weakened with the increasing shell thickness. The SERS intensity of these AucoreCoshell nanoparticles is found to be about twenty times higher than that obtained on an electrochemically roughened cobalt electrode.
