摘要：A 7.8-μm surface emitting second-order distributed feedback quantum cascade laser （DFB QCL） structure with metallized surface grating is studied. The modal property of this structure is described by utilizing coupled-mode theory where the coupling coefficients are derived from exact Floquet-Bloch solutions of infinite periodic structure. Based on this theory, the influence of waveguide structure and grating topography as well as device length on the laser performance is numerically investigated. The optimized surface emitting second-order DFB QCL structure design exhibits a high surface outcoupling efficiency of 22% and a low threshold gain of 10 cm-1. Using a π phase-shift in the centre of the grating, a high-quality single-lobe far-field radiation pattern is obtained.

摘要：For about three decades, DNA-based nanotechnology has been undergoing development as an assembly method for nanostructured materials. The DNA origami method pioneered by Rothemund paved the way for the formation of 3D structures using DNA self assembly. The origami approach uses a long scaffold strand as the input for the self assembly of a few hundred staple strands into desired shapes. Herein, we present a 3D origami "roller" (75 nm in length) designed using caDNAno software. This has the potential to be used as a template to assemble nanoparticles into different pre-defined shapes. The "roller" was characterized with agarose gel electrophoresis, atomic force microscopy (AFM) and transmission electron microscopy (TEM).

摘要：在多道次普旋成形中,多采用往程和回程结合的旋轮轨迹形式来提高材料的成形性能。为了深入探究回程旋压,对2024-O铝合金半球件回程旋压轨迹进行研究。基于二次Bezier曲线,建立普旋回程旋轮轨迹的参数化设计方法;并结合有限元技术,分析回程轨迹参数对2024-O铝合金半球件旋压应力、应变和减薄率的影响规律。通过对回程旋压的仿真分析,揭示回程的应力和应变特点。结果表明,回程道次的使用可以明显提高铝合金球面件的壁厚均匀性;同时,揭示了Bezier曲线参数化选择与旋压厚度均匀性的关系。

摘要：A synthetic medium for ethanol production by recombinant xylose-fermenting Zymomonas mobilis was optimized using Plackett-Burman(PB) design and response surface methodology(RSM).The effects of 19 medium components were investigated by PB *** of these components were determined to have significant effects on ethanol *** statistical model was constructed via central composite design(CCD) using five selected variables,including xylose,trisodium citrate,choline chloride,pyridoxine,and *** validity of the developed model was *** ethanol concentration in the optimized medium was 6.7% higher than in the RM *** optimized medium was then simplified to give the final synthetic medium(S2),in which the ethanol concentration was 20.7% higher than in the RM *** and trisodium citrate were the key medium components influencing ethanol production,while calcium pantothenate was the only growth factor required by recombinant *** production and growth response were directly proportional to the logarithm of the concentration of trisodium citrate in the range of 0.1-1.6 g/L.

摘要：The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances between the inlet guide vanes and the impeller inlet of 280 mm, 380 mm and 460 mm. The efficiency-flow curves and the characteristic curves were obtained for the pump for various operation conditions. The experiment results demonstrated that the pre-whirl regulation widened the high efficiency zone and improved the hydraulic performance for off-design conditions with the proper pre-whirl angle. The axial distance between the inlet guide vanes and the impeller inlet influenced the pre-whirl regulation effect of the inlet guide vanes with the best pre-whirl regulation effect obtained for an axial distance of 380 mm. These results showed that an appropriate axial distance between the inlet guide vanes and the impeller inlet can improve the fluid flow at the impeller entrance with pre-whirl regulation for centrifugal pumps.

摘要：在TBM掘进过程中,出碴槽布置直接影响刀盘出碴性能。为了提高TBM的出碴性能,对出碴槽最优布置进行了研究。采用离散元方法对TBM出碴过程进行数值模拟,包括岩碴掉落、与滚刀碰撞、被铲刀铲起以及运送到皮带机排出的全过程。基于吉林输水隧道工程的岩碴样本进行粒径分布分析,建立岩碴颗粒模型,得到出碴槽数量和相邻出碴槽间隔角度对出碴性能的影响规律。结果表明,当出碴槽数量从4个增加至8个时,出碴量增加了29%,残余岩碴量减少40.5%且出碴过程更稳定。出碴量随出碴槽间隔角度的变化不大,但残余出碴量随着间隔角度的增大而逐渐增多。根据仿真研究,得到了该隧道工程刀盘出碴槽的最优布置方案,并通过隧道实际施工数据验证了优化后TBM的出碴性能。

摘要：为了提高连续熔铸与定向凝固用冷坩埚的工作效率和优化结构设计,基于实验验证,建立了不同结构的电磁冷坩埚的3D有限元模型,并研究了坩埚结构对其内部磁场的影响规律。电磁冷坩埚的结构变量包括坩埚内径、坩埚壁厚、开缝形状以及水冷铜环。结果表明:随着坩埚内径的减小、开缝宽度和横截面积的增大以及水冷铜环的去除,坩埚内分瓣中点和开缝处的磁场随之增强。此外,当外径一定时,存在一个最差的坩埚壁厚使得坩埚内磁场值最低。

摘要：设计制造了一台推力为500 N的液氧气甲烷模型发动机,对其开展了一系列点火试验,火花塞的安装位置分头部与身部两种情况。结果表明,当使用头部火花塞点火时,发动机内的推进剂可以正常起火但火焰无法持续稳定,这主要是因为火花塞末端被置于喷雾浓度与气流速度均较低的区域,使得这个区域内产生的火焰无法为整个发动机提供足够的点火能量。然而,当使用身部火花塞时,发动机内的推进剂可以同时实现可靠点火与稳定燃烧,这主要是因为在身部,二种推进剂浓度与流速均足够。当氧燃混合比从2.61增加到3.49时,试验得到的燃烧室压力从0.474 MPa增加到0.925 MPa,同时燃烧效率从57.8%增加到95.1%,这主要是因为喷注器配置,导致在低工况下液氧无法得到充分破碎。

摘要：A new multi-functional bridge seismic isolation bearing(MFBSIB) is designed and its mechanical model is developed in this *** an upper sliding device and a lower energy dispassion isolation device effectively,the new MFBSIB can adjust the deformation caused by temperature,vehicle breaks,and concrete creep,etc.,in addition to dissipating *** switch of 'slide-isolation' is achieved and the efficiency of both upper and lower parts is validated through experiment with a *** shear performance curve established in this paper is verified to be efficient in describing the mechanical characteristics of the bearing through *** is proved through both numerical calculation and experimental analysis that the new MFBSIB is endowed with enough vertical rigidity,good energy dissipation ability,stable overall performance,and good realization in expected *** performance is slightly influenced by shear stress,while affected by vertical pressure,loading frequency,slide limit,etc.,*** results could provide reference for study and application of the new MFBSIB.

摘要：The emergence of nanoparticles(NPs)has attracted tremendous interest of the scientific community for decades due to their unique properties and potential applications in diverse areas,including drug delivery and *** novel NPs have been synthesized and used to reduce drug toxicity,improve bio-availability,prolong circulation time,control drug release,and actively target to desired cells or ***,clinical translation of NPs with the goal of treating particularly challenging diseases,such as cancer,will require a thorough understanding of how the NP properties influence their fate in biological systems,especially in *** efforts have been paid to studying the interactions and mechanisms of NPs and *** deliberately designed,the NPs in contact with biological fluids are rapidly covered by a selected group of biomolecules especially proteins to form a corona that interacts with biological *** this view,the recent development of NPs in drug delivery and the interactions of NPs with cells and proteins are *** understanding the protein-NP interactions,some guidelines for safety design of NPs,challenges and future perspectives are discussed.