This paper presented an effective shielding design of magnetic fields generated by unidirectional current. Theoretical formulas and numerical computation software based on boundary element method (BEM) are employed to...This paper presented an effective shielding design of magnetic fields generated by unidirectional current. Theoretical formulas and numerical computation software based on boundary element method (BEM) are employed to evaluate the shielding effectiveness (SE) of cylindrical shell. It is shown that ungrounded or one end grounded metal shell is ineffective for such magnetic fields. SE can be obtained by connecting the two ends of the conducting shell with low impedance connector, or alternatively, grounding the two ends. The experimental results also support these conclusions.展开更多
The modern landmine's electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse(UWB-EMP). The finite-difference time-domain(FDTD) method in lossy me...The modern landmine's electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse(UWB-EMP). The finite-difference time-domain(FDTD) method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface(MPI) parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.展开更多
With Ti(SO4)2, SnC14-5H20 and urea as raw materials, SnO2-TiO2 nanocomposites were synthesized via low temperature hydrothermal method at 80--100℃ in aqueous solutions. The morphologies of the products were altered...With Ti(SO4)2, SnC14-5H20 and urea as raw materials, SnO2-TiO2 nanocomposites were synthesized via low temperature hydrothermal method at 80--100℃ in aqueous solutions. The morphologies of the products were altered systematically by varying the Ti/Sn molar ratio of the reactants, and rutile-phase particles were obtained with an average diameter of about 52.2 nm at a molar ratio of Ti/Sn=7.5. The surface composition of the composite was revealed by X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD) to be solely TiO2 with a rutile structure. This new composite material exhibits a high ultraviolet absorption capacity, and its photocatalytic activity for phenol oxidation is much lower than that of the commercial titania nanoparticles(P25).展开更多
The Shielding coefficient of superconductor in the shape of the spherical shell is derived on the basis of Maxwell's equations and London's two-liquid model. Some cases of superconductor shielding have also ...The Shielding coefficient of superconductor in the shape of the spherical shell is derived on the basis of Maxwell's equations and London's two-liquid model. Some cases of superconductor shielding have also been discussed in this paper.展开更多
为了解决手机芯片屏蔽壳表面白印缺陷微小、尺度各异等因素影响检测快速性和准确性的问题,本文提出一种基于长短连接通路和双注意力网络(long short link and double attention network,LSDANet)的手机芯片屏蔽壳表面缺陷检测方法。首先...为了解决手机芯片屏蔽壳表面白印缺陷微小、尺度各异等因素影响检测快速性和准确性的问题,本文提出一种基于长短连接通路和双注意力网络(long short link and double attention network,LSDANet)的手机芯片屏蔽壳表面缺陷检测方法。首先,通过构建基于编码和解码的语义分割模型和利用长短距离连接通路,提高网络模型对尺度各异缺陷的特征提取能力。其次,分别设计基于通道和空间的注意力机制,增大5—10pixel尺寸的白印缺陷在空间和通道上的特征权重。最后,融合双注意力机制和长短距离连接通路分割模型,构建LSDANet缺陷检测网络,应用于手机芯片屏蔽壳表面缺陷检测。实验数据表明,LSDANet网络能够达到96.21%的平均像素精度、66.13%的平均交并比和39.03的每秒检测帧数,相比多种语义分割算法均具有更高的检测精度和速度。展开更多
A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly invol...A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core–shell particles by a controllable liquid reduced reaction of Ag[(NH3)2]+ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy (SEM), transmitted electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.展开更多
文摘This paper presented an effective shielding design of magnetic fields generated by unidirectional current. Theoretical formulas and numerical computation software based on boundary element method (BEM) are employed to evaluate the shielding effectiveness (SE) of cylindrical shell. It is shown that ungrounded or one end grounded metal shell is ineffective for such magnetic fields. SE can be obtained by connecting the two ends of the conducting shell with low impedance connector, or alternatively, grounding the two ends. The experimental results also support these conclusions.
基金Project supported by the Postdoctoral Science Foundation of China(Grant No.2014M552610)
文摘The modern landmine's electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse(UWB-EMP). The finite-difference time-domain(FDTD) method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface(MPI) parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.
文摘With Ti(SO4)2, SnC14-5H20 and urea as raw materials, SnO2-TiO2 nanocomposites were synthesized via low temperature hydrothermal method at 80--100℃ in aqueous solutions. The morphologies of the products were altered systematically by varying the Ti/Sn molar ratio of the reactants, and rutile-phase particles were obtained with an average diameter of about 52.2 nm at a molar ratio of Ti/Sn=7.5. The surface composition of the composite was revealed by X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD) to be solely TiO2 with a rutile structure. This new composite material exhibits a high ultraviolet absorption capacity, and its photocatalytic activity for phenol oxidation is much lower than that of the commercial titania nanoparticles(P25).
文摘The Shielding coefficient of superconductor in the shape of the spherical shell is derived on the basis of Maxwell's equations and London's two-liquid model. Some cases of superconductor shielding have also been discussed in this paper.
文摘为了解决手机芯片屏蔽壳表面白印缺陷微小、尺度各异等因素影响检测快速性和准确性的问题,本文提出一种基于长短连接通路和双注意力网络(long short link and double attention network,LSDANet)的手机芯片屏蔽壳表面缺陷检测方法。首先,通过构建基于编码和解码的语义分割模型和利用长短距离连接通路,提高网络模型对尺度各异缺陷的特征提取能力。其次,分别设计基于通道和空间的注意力机制,增大5—10pixel尺寸的白印缺陷在空间和通道上的特征权重。最后,融合双注意力机制和长短距离连接通路分割模型,构建LSDANet缺陷检测网络,应用于手机芯片屏蔽壳表面缺陷检测。实验数据表明,LSDANet网络能够达到96.21%的平均像素精度、66.13%的平均交并比和39.03的每秒检测帧数,相比多种语义分割算法均具有更高的检测精度和速度。
基金Supported by the National High Technology Research and Development Program of China (No. 2006AA03Z461)the National Defense Fundamental Scientific Research Program (No. A1420080185)
文摘A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core–shell particles by a controllable liquid reduced reaction of Ag[(NH3)2]+ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy (SEM), transmitted electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.