Although existing hydraulic models have been used to simulate and predict urban flooding, most of these models are inadequate due to the high spatial resolution required to simulate flows in urban floodplains. Nesting...Although existing hydraulic models have been used to simulate and predict urban flooding, most of these models are inadequate due to the high spatial resolution required to simulate flows in urban floodplains. Nesting high-resolution subdomains within coarser-resolution models is an efficient solution for enabling simultaneous calculation of flooding due to tides, surges, and high river flows. MSN_Flood has been developed to incorporate moving boundaries around nested domains, permitting alternate flooding and drying along the boundary and in the interior of the domain. Ghost cells adjacent to open boundary cells convert open boundaries, in effect, into internal boundaries. The moving boundary may be multi-segmented and non-continuous, with recirculating flow across the boundary. When combined with a bespoke adaptive interpolation scheme, this approach facilitates a dynamic internal boundary. Based on an alternating-direction semi-implicit finite difference scheme,MSN_Flood was used to hindcast a major flood event in Cork City resulting from the combined pressures of fluvial, tidal, and storm surge processes. The results show that the model is computationally efficient, as the 2-m high-resolution nest is used only in the urban flooded region.Elsewhere, lower-resolution nests are used. The results also show that the model is highly accurate when compared with measured data. The model is capable of incorporating nested sub-domains when the nested boundary is multi-segmented and highly complex with lateral gradients of elevation and velocities. This is a major benefit when modelling urban floodplains at very high resolution.展开更多
A vortex domain wall's(VW) magnetic racetrack memory's high performance depends on VW structural stability,high speed, low power consumption and high storage density. In this study, these critical parameters w...A vortex domain wall's(VW) magnetic racetrack memory's high performance depends on VW structural stability,high speed, low power consumption and high storage density. In this study, these critical parameters were investigated in magnetic multi-segmented nanowires using micromagnetic simulation. Thus, an offset magnetic nanowire with a junction at the center was proposed for this purpose. This junction was implemented by shifting one portion of the magnetic nanowire horizontally in the x-direction(l) and vertically(d) in the y-direction. The VW structure became stable by manipulating magnetic properties, such as magnetic saturation(M_(4)) and magnetic anisotropy energy(K_(u)). In this case, increasing the values of M_(4) ≥ 800 kA/m keeps the VW structure stable during its dynamics and pinning and depinning in offset nanowires,which contributes to maintenance of the storage memory's lifetime for a longer period. It was also found that the VW moved with a speed of 500 m/s, which is desirable for VW racetrack memory devices. Moreover, it was revealed that the VW velocity could be controlled by adjusting the offset area dimensions(l and d), which helps to drive the VW by using low current densities and reducing the thermal-magnetic spin fluctuations. Further, the depinning current density of the VW(J_(d)) over the offset area increases as d increases and l decreases. In addition, magnetic properties, such as the M_(4) and K_(u),can affect the depinning process of the VW through the offset area. For high storage density, magnetic nanowires(multisegmented) with four junctions were designed. In total, six states were found with high VW stability, which means three bits per cell. Herein, we observed that the depinning current density(J_(d)) for moving the VW from one state to another was highly influenced by the offset area geometry(l and d) and the material's magnetic properties, such as the M_(4) and K_(u).展开更多
This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical simulations.Multi-segmented grain is composed of several thin grains with two or...This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical simulations.Multi-segmented grain is composed of several thin grains with two or more ports.The numerical model consists of Navier-Stokes equations with turbulence,solid fuel pyrolysis,chemical reactions,a fluid–solid coupling model and a regression rate model.The simulations adopt 90%Hydrogen Peroxide(HP)and PolyEthylene(PE)as the propellant combination.The effects of the rotation,port number,fuel grain segment number and mid-chamber length on the flow field and combustion performances are analyzed.The results indicate that the multi-segmented grain configuration can strengthen the flow field,and the regression rate and combustion efficiency are enhanced.Take the cases with two grain segments and three ports for example,the regression rate is increased by 32.4%-45.1%and the combustion efficiency increases by 6%-8.6%in different rotation angles.展开更多
A novel flat-flat resonator consisting of two crystals（Nd：YAG ＋ Nd：YVO4） is established for power scaling in a diode-end-pumped solid-state laser. We systematically compare laser characteristics between multi-seg...A novel flat-flat resonator consisting of two crystals（Nd：YAG ＋ Nd：YVO4） is established for power scaling in a diode-end-pumped solid-state laser. We systematically compare laser characteristics between multi-segmented（Nd：YAG ＋ Nd：YVO4） and conventional composite（Nd：YAG ＋ Nd：YAG） crystals to demonstrate the feasibility of spectral line matching for output power scale-up in end-pumped lasers. A maximum continuous-wave output power of 79.2 W is reported at 1064 nm, with Mx2= 4.82, My2= 5.48, and a pumping power of 136 W in the multi-segmented crystals（Nd：YAG ＋ Nd：YVO4）. Compared to conventional composite crystals（Nd：YAG ＋ Nd：YAG）, the optical-optical conversion efficiency of multi-segmented crystals（Nd：YAG ＋ Nd：YVO4） from 808 nm to 1064 nm is enhanced from 30% to 58.8%,while the laser output sensitivity as affected by the diode-laser temperature is reduced from 55% to 9%.展开更多
[目的]通过分析比较对治疗多节段脊髓型颈椎病的两种前路术式进行探讨研究。[方法]回顾性分析2008年1月一2011年8月手术治疗的65例三节段脊髓型颈椎病患者的临床资料，根据手术方式不同分为2组：前路椎间盘切除减压融合术组（anterior c...[目的]通过分析比较对治疗多节段脊髓型颈椎病的两种前路术式进行探讨研究。[方法]回顾性分析2008年1月一2011年8月手术治疗的65例三节段脊髓型颈椎病患者的临床资料，根据手术方式不同分为2组：前路椎间盘切除减压融合术组（anterior cervical discectomy with fusion，ACDF）（A组）、前路椎体切除减压融合术组（anterior cervical corpectomy with fusion，ACCF）（B组），其中A组男性20例，女性7例；平均年龄（50．43±6．50）岁；B组男性25例，女性13例；平均年龄（52．31±7．32）岁；评估2种术式围手术期并发症的发生率、手术时间、手术出血量及神经功能改善率、生理弧度改善情况。[结果]随访时间13—34个月，平均20个月。共有7例在手术后出现多种并发症，包括植骨未融合2例（B组）（5．26％），B组植骨不愈合发生率显著高于A组（P〈0．05）；声音嘶哑1例，其中B组l例（2．63％）；吞咽困难2例，其中A组1例（3．70％），B组1例（2．63％）；脑脊液漏1例（A组）；切口感染1例（B组）。A组患者并发症发生率为7．40％，B组为13．15％，B组患者术后并发症的发生率显著高于A组（P〈0．05）。两组手术时间分别为（107．9±32．4）min、（129±23）min，两组间比较差异有统计学意义（P〈0．05）；神经功能平均改善率分别为55．3％和56．9％，两组间比较差异无统计学意义（P〉0．05）；A组手术前颈椎融合节段Cobb角为（7．78±1．15）°，末次随访时Cobb角为（15．82±3．27）°；B组手术前颈椎融合节段Cobb角为（8．36±2．57）°，末次随访时Cobb角为（12．69±2．96）°；术后颈椎生理曲度均得到明显改善，但A组明显优于B组，两组间比较差异有统计学意义（P〈0．05）。[结论]两种手术方法治疗多节段脊髓型颈椎病均可取得满意的疗效，但ACDF具有并发症发生率低、出血量少、手术展开更多
文摘Although existing hydraulic models have been used to simulate and predict urban flooding, most of these models are inadequate due to the high spatial resolution required to simulate flows in urban floodplains. Nesting high-resolution subdomains within coarser-resolution models is an efficient solution for enabling simultaneous calculation of flooding due to tides, surges, and high river flows. MSN_Flood has been developed to incorporate moving boundaries around nested domains, permitting alternate flooding and drying along the boundary and in the interior of the domain. Ghost cells adjacent to open boundary cells convert open boundaries, in effect, into internal boundaries. The moving boundary may be multi-segmented and non-continuous, with recirculating flow across the boundary. When combined with a bespoke adaptive interpolation scheme, this approach facilitates a dynamic internal boundary. Based on an alternating-direction semi-implicit finite difference scheme,MSN_Flood was used to hindcast a major flood event in Cork City resulting from the combined pressures of fluvial, tidal, and storm surge processes. The results show that the model is computationally efficient, as the 2-m high-resolution nest is used only in the urban flooded region.Elsewhere, lower-resolution nests are used. The results also show that the model is highly accurate when compared with measured data. The model is capable of incorporating nested sub-domains when the nested boundary is multi-segmented and highly complex with lateral gradients of elevation and velocities. This is a major benefit when modelling urban floodplains at very high resolution.
文摘A vortex domain wall's(VW) magnetic racetrack memory's high performance depends on VW structural stability,high speed, low power consumption and high storage density. In this study, these critical parameters were investigated in magnetic multi-segmented nanowires using micromagnetic simulation. Thus, an offset magnetic nanowire with a junction at the center was proposed for this purpose. This junction was implemented by shifting one portion of the magnetic nanowire horizontally in the x-direction(l) and vertically(d) in the y-direction. The VW structure became stable by manipulating magnetic properties, such as magnetic saturation(M_(4)) and magnetic anisotropy energy(K_(u)). In this case, increasing the values of M_(4) ≥ 800 kA/m keeps the VW structure stable during its dynamics and pinning and depinning in offset nanowires,which contributes to maintenance of the storage memory's lifetime for a longer period. It was also found that the VW moved with a speed of 500 m/s, which is desirable for VW racetrack memory devices. Moreover, it was revealed that the VW velocity could be controlled by adjusting the offset area dimensions(l and d), which helps to drive the VW by using low current densities and reducing the thermal-magnetic spin fluctuations. Further, the depinning current density of the VW(J_(d)) over the offset area increases as d increases and l decreases. In addition, magnetic properties, such as the M_(4) and K_(u),can affect the depinning process of the VW through the offset area. For high storage density, magnetic nanowires(multisegmented) with four junctions were designed. In total, six states were found with high VW stability, which means three bits per cell. Herein, we observed that the depinning current density(J_(d)) for moving the VW from one state to another was highly influenced by the offset area geometry(l and d) and the material's magnetic properties, such as the M_(4) and K_(u).
文摘This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical simulations.Multi-segmented grain is composed of several thin grains with two or more ports.The numerical model consists of Navier-Stokes equations with turbulence,solid fuel pyrolysis,chemical reactions,a fluid–solid coupling model and a regression rate model.The simulations adopt 90%Hydrogen Peroxide(HP)and PolyEthylene(PE)as the propellant combination.The effects of the rotation,port number,fuel grain segment number and mid-chamber length on the flow field and combustion performances are analyzed.The results indicate that the multi-segmented grain configuration can strengthen the flow field,and the regression rate and combustion efficiency are enhanced.Take the cases with two grain segments and three ports for example,the regression rate is increased by 32.4%-45.1%and the combustion efficiency increases by 6%-8.6%in different rotation angles.
基金Project supported by the National Defense Pre-Research Foundation of China(Grant No.9140A020105)
文摘A novel flat-flat resonator consisting of two crystals（Nd：YAG ＋ Nd：YVO4） is established for power scaling in a diode-end-pumped solid-state laser. We systematically compare laser characteristics between multi-segmented（Nd：YAG ＋ Nd：YVO4） and conventional composite（Nd：YAG ＋ Nd：YAG） crystals to demonstrate the feasibility of spectral line matching for output power scale-up in end-pumped lasers. A maximum continuous-wave output power of 79.2 W is reported at 1064 nm, with Mx2= 4.82, My2= 5.48, and a pumping power of 136 W in the multi-segmented crystals（Nd：YAG ＋ Nd：YVO4）. Compared to conventional composite crystals（Nd：YAG ＋ Nd：YAG）, the optical-optical conversion efficiency of multi-segmented crystals（Nd：YAG ＋ Nd：YVO4） from 808 nm to 1064 nm is enhanced from 30% to 58.8%,while the laser output sensitivity as affected by the diode-laser temperature is reduced from 55% to 9%.
文摘[目的]通过分析比较对治疗多节段脊髓型颈椎病的两种前路术式进行探讨研究。[方法]回顾性分析2008年1月一2011年8月手术治疗的65例三节段脊髓型颈椎病患者的临床资料，根据手术方式不同分为2组：前路椎间盘切除减压融合术组（anterior cervical discectomy with fusion，ACDF）（A组）、前路椎体切除减压融合术组（anterior cervical corpectomy with fusion，ACCF）（B组），其中A组男性20例，女性7例；平均年龄（50．43±6．50）岁；B组男性25例，女性13例；平均年龄（52．31±7．32）岁；评估2种术式围手术期并发症的发生率、手术时间、手术出血量及神经功能改善率、生理弧度改善情况。[结果]随访时间13—34个月，平均20个月。共有7例在手术后出现多种并发症，包括植骨未融合2例（B组）（5．26％），B组植骨不愈合发生率显著高于A组（P〈0．05）；声音嘶哑1例，其中B组l例（2．63％）；吞咽困难2例，其中A组1例（3．70％），B组1例（2．63％）；脑脊液漏1例（A组）；切口感染1例（B组）。A组患者并发症发生率为7．40％，B组为13．15％，B组患者术后并发症的发生率显著高于A组（P〈0．05）。两组手术时间分别为（107．9±32．4）min、（129±23）min，两组间比较差异有统计学意义（P〈0．05）；神经功能平均改善率分别为55．3％和56．9％，两组间比较差异无统计学意义（P〉0．05）；A组手术前颈椎融合节段Cobb角为（7．78±1．15）°，末次随访时Cobb角为（15．82±3．27）°；B组手术前颈椎融合节段Cobb角为（8．36±2．57）°，末次随访时Cobb角为（12．69±2．96）°；术后颈椎生理曲度均得到明显改善，但A组明显优于B组，两组间比较差异有统计学意义（P〈0．05）。[结论]两种手术方法治疗多节段脊髓型颈椎病均可取得满意的疗效，但ACDF具有并发症发生率低、出血量少、手术
