W波段TE6,2模同轴开放式谐振腔的研究与设计

详细研究了一种用于回旋管冷测的三段式同轴谐振腔模式激励器,该模式激励器利用同轴开放腔的选频选模特性将输入的W波段的波功率转换为TE6,2模式输出。基于缓变截面波导理论,研究了同轴谐振腔激励TE6,2模式的机理;求解了同轴波导中TE模式的特征根和不均匀弦方程并得到腔体谐振频率及Q值;分析了同轴腔内外半径对谐振频率的影响;给出了W波段高纯度TE6,2模谐振腔优化设计的参数;并用电磁仿真软件对其进行仿真计算,结果表明:该谐振腔的TE6,2模式纯度达到99.51%。     

W波段共焦波导回旋行波管色散特性和衍射损耗研究

从共焦波导的电磁场分布出发,得到共焦波导的色散方程和衍射损耗方程。使用数值分析软件MATLAB对W波段共焦波导回旋行波管高频结构的色散特性和衍射损耗进行理论计算,并且绘制了色散曲线和衍射损耗曲线。利用HFSS电磁仿真软件,采用本征模的求解方法,把主从边界条件应用在共焦波导结构上,对其色散特性进行仿真计算,使用场求解器,仿真计算其衍射损耗率。理论计算和仿真结果相互吻合。     

左手材料对谐振腔内部电磁场分布的影响

在谐振腔的设计过程中,由于填充介质引起的损耗以及模式干扰导致谐振腔内部电磁场分布的优化受到限制,因而使得设计高品质因数的谐振腔变得困难。根据"左手材料"的特殊性质,运用电动力学理论对谐振腔内部电磁场分布进行计算研究,通过high frequency structure simulator(简称HFSS)仿真软件对谐振腔内的场分布进行模拟。计算结果显示,左手材料的填充可以改善谐振腔内部电磁场的分布。相对于传统材料而言,左手材料的填充可以使谐振腔内部中心部位的电磁场分布集中、电磁场强度增加,其中,电场强度可达到3.5009×10-1 V/m,比真空情况提高了13%,比填充空气时提高了4%;磁场强度可达到5.8722×10-3 A/m,比真空时提高了156%,比填充空气时提高了134%,高频仿真器的仿真数据与以上结果相吻合。该方法克服了传统材料对谐振腔内电磁场分布优化的局限性,为设计新型的谐振腔提供了一定的理论指导作用。     

铸造材料伸缩尾翼气动载荷下接触问题的分析与研究

采用有限元技术,应用MSC仿真软件分析铸造材料伸缩结构尾翼在弹道飞行过程中气动载荷矩阵作用下的接触应力问题.通过建立计算模型,施加边界条件及启动接触非线性求解器进行求解,得到尾翼三维结构下的位移和应力情况,该种MD Nastran隐式非线性求解器SOL600计算方法能够充分模拟实际三维结构的接触问题.     

管材无模成形温度场的数值模拟及分析

采用有限单元法并结合有限元分析软件,对管材无模成形时管材温度场进行数值模拟研究,得到管材无模拉伸变形过程中温度场分布规律,并对影响温度场的因素加以分析,如冷热源间距、冷热源移动速度、加载时间分别对温度场分布的影响,该模拟结果与实验结果相吻合.     

Ka波段TE01模回旋行波管宽带输入耦合器的设计

Ka波段TE01模回旋行波管的输入耦合器将矩形波导中输入的TE10模转化为圆波导中TE01模的行波场,以实现对回旋电子注角向速度的调制。本文首先对Ka波段TE01模回旋行波管的输入耦合器进行了解析分析和数值计算。通过数值计算得到输入耦合器的初步结构和尺寸,然后利用三维高频分析软件HFSS进行精确的模拟和修正。通过优化设计在Ka波段获得了3 dB带宽约为3 GHz,1 dB带宽大于2GHz的高性能TE1□0-TE4◎11-TE0○1输入耦合器和3 dB带宽约为3.5 GHz,1 dB带宽约为3 GHz的高性能TE1□0-TE5◎11-TE0○1输入耦合器。冷测实验研究表明优化设计结果与冷测结果相吻合。     

锥形聚音器声传播特性研究

为了研究声信号在聚音器中的传播特性与内壁损耗问题,采用理论分析和数值模拟相结合的方法.根据韦伯斯特理论和别洛夫声衰减原理,理论求解出聚音器对声压的放大倍数和内壁声损耗量.利用有限元软件,建立了锥形聚音器有限元模型,将硬声场边界条件下声压放大倍数作为研究基准,计算钢、铝、聚苯乙烯、尼龙4种声阻抗条件下聚音器内壁声损耗.结果表明,数值模拟与理论分析相吻合,研究得出材料声阻抗减小,聚音器内壁声损耗增大,对声压的放大倍数减小.     

左手材料对介质谐振腔谐振参数的影响

"左手材料"是与传统材料性质相悖的另外一种材料。根据"左手材料"的特殊性质,采用理论计算与模拟仿真相结合的方法,对影响谐振腔谐振参数的因素进行分析,得出了填充介质的材料属性与谐振腔品质因数、谐振频率的关系。结果显示,"左手材料"的填充,会影响谐振腔的品质因数,相较于介电常数,材料磁导率的作用效果更明显;"左手材料"可以在不改变谐振腔尺寸的基础上提高谐振频率。这相较于传统理论而言有了进一步的进展,为探索和设计新颖的谐振腔提供了理论依据。     

一种高效的宽带简正波本征值计算方法

为提高宽带简正波本征值的计算效率,汉密尔顿方法通过公式变换抵消频率项,将宽带简正波本征值的计算由频率、本征值实部和虚部的三维寻根降低至本征值实部和虚部的二维寻根,可以一次性求解单号简正波所有频率对应的简正波本征值。在已有工作的基础上优化和完善了汉密尔顿宽带简正波本征值算法,并加入并行计算方法进一步提高计算效率。以简正波模型KRAKENC作为对比,通过若干数值算例验证了该算法对于宽带简正波本征值的计算精度和计算效率。数值仿真结果显示,在保证宽带简正波本征值计算精度的前提下,该方法的计算效率相对KRAKENC有着明显的优势;加入并行算法后,该方法的计算效率得到大幅提高。     

基于复等效源法与最速下降的广义逆波束形成

针对指向性声源定位问题,提出一种基于复等效源法与最速下降相结合的广义逆波束形成方法。该方法首先将声场分解成一系列本征模态,然后利用复等效源拟合各阶本征模态,并通过残差梯度范数最小化迭代求解源强,最后通过本征模态叠加实现声场成像。通过圆形活塞声源和偶极子声源仿真,验证了该方法的有效性。与L1范数广义逆波束形成方法相比,该方法具有更好的聚焦性和更高的分辨率。实验结果进一步证明了该方法的有效性和优越性。     

Hollow fibres with walls filled with hydrogels

Although extractions using hollow fibres can be faster and more efficient than those carried out in more conventional equipment, such as mixer/separators, accidental convection through the pores in the fibre walls can compromise these advantages. A way of overcoming this drawback is to fill the walls of the fibres with a gel, such as crosslinked polyvinyl alcohol. The overall mass transfer is unaltered but the convection through the pores is eliminated.     

Out with the old in with the new

The materials issues facing the microelectromechanical systems (MEMS) community can be understood best in terms of the historical context. The field began almost as an afterthought among those engaged in integrated circuit production. These researchers recognized early on that the same processes used in the production of circuits could be re-ordered to make very small mechanical devices. The huge investment made by the electronics community in silicon technologies — and the relative ease with which these techniques could be adapted to device production — made them an obvious resource for early MEMS designers. It is no accident that polycrystalline silicon is the most commonly used structural material.But with the continued expansion of MEMS devices into new areas of application, the limitations of silicon (Si) usefulness became clear. The need to combine electronics and MEMS on the same chip (iMEMS), improve the wear characteristics of moving parts, and achieve a greater mass of moving parts in MEMS inertial sensors have led researchers away from a ‘one-material-fits-all’ approach. Instead the search is on for materials that more directly serve specific ends. The need for biocompatibility in the emerging field of bio-MEMS has added urgency to the quest for new materials, since Si-based materials cannot meet every bio-MEMS need.     

用心感知生活用感知抒写创意

前几天妹妹在我的"世界之星"颁奖仪式的照片下留言说:"哥,我没想过你的人生会这么精彩!",是啊,连我自己也从未想过我的人生能如此丰富多彩. 很多设计师是因为喜欢美术或是因为从小便培养的美术基础才选择美术专业,跟别人不同,美术是我不高的文化分数无奈之下的选择,万幸的是当我接触它时,便狂热地爱上了它.     

Writing with Fluid: Structuring Hydrogels with Micrometer Precision by AFM in Combination with Nanofluidics

Hydrogels have many applications in biomedical surface modification and tissue engineering. However, the structuring of hydrogels after their formation represents still a major challenge, in particular due to their softness. Here, a novel approach is presented that is based on the combination of atomic force microscopy (AFM) and nanofluidics, also referred to as FluidFM technology. Its applicability is demonstrated for supramolecular hydrogel films that are prepared from low‐molecular weight hydrogelators, such as derivates of 1,3,5‐benzene tricarboxamides (BTAs). BTA films can be dissolved selectively by ejecting alkaline solution through the aperture of a hollow AFM‐cantilever connected to a nanofluidic controller. The AFM‐based force control is essential in preventing mechanical destruction of the hydrogels. The resulting “chemical writing” process is studied in detail and the influence of various parameters, such as applied pressure and time, is validated. It is demonstrated that the achievable structuring precision is primarily limited by diffusion and the aperture dimensions. Recently, various additive techniques have been presented to pattern hydrogels. The here‐presented subtractive approach can not only be applied to structure hydrogels from the large class of reversibly formed gels with superior resolution but would also allow for the selective loading of the hydrogels with active substances or nanoparticles.     

Bridge circuits with pulse supply with extended functional capabilities

Bridge circuits with considerably extended functional capabilities are considered. They enable one, without any change in configuration, to determine the parameters of RL, RC, and RCL multicomponent two-terminal networks when connected to the same two leadouts of the bridge circuits. Translated from Izmeritel’naya Tekhnika, No. 4, pp. 40–45, April, 2009.     

Accommodation with higher-order monochromatic aberrations corrected with adaptive optics

Higher-order monochromatic aberrations in the human eye cause a difference in the appearance of stimuli at distances nearer and farther from best focus that could serve as a signed error signal for accommodation. We explored whether higher-order monochromatic aberrations affect the accommodative response to 0.5 D step changes in vergence in experiments in which these aberrations were either present as they normally are or removed with adaptive optics. Of six subjects, one could not accommodate at all for steps in either condition. One subject clearly required higher-order aberrations to accommodate at all. The remaining four subjects could accommodate in the correct direction even when higher-order aberrations were removed. No subjects improved their accommodation when higher-order aberrations were corrected, indicating that the corresponding decrease in the depth of field of the eye did not improve the accommodative response. These results are consistent with previous findings of large individual differences in the ability to accommodate in impoverished conditions. These results suggest that at least some subjects can use monochromatic higher-order aberrations to guide accommodation. They also show that some subjects can accommodate correctly when higher-order monochromatic aberrations as well as established cues to accommodation are greatly reduced.     

Vehicle routing problem with vector profits with max-min criterion

This article introduces a new routing problem referred to as the vehicle routing problem with vector profits. Given a network composed of nodes (depot/sites) and arcs connecting the nodes, the problem determines routes that depart from the depot, visit sites to collect profits, and return to the depot. There are multiple stakeholders interested in the mission and each site is associated with a vector whose kth element represents the profit value for the kth stakeholder. The objective of the problem is to maximize the profit sum for the least satisfied stakeholder, i.e. the stakeholder with the smallest total profit value. An approach based on linear programming relaxation and column-generation to solve this max–min type routing problem was developed. Two case studies—the planetary surface exploration and the Rome tour cases—were presented to demonstrate the effectiveness of the proposed problem formulation and solution methodology.     

Acute hemolysis with acute renal failure in a patient with valproic acid poisoning treated with charcoal hemoperfusion

Hemoperfusion consists of the passage of anticoagulated blood through a column containing adsorbent particles. It was introduced in 1940 and refined from 1950 to 1970, and then introduced clinically for the treatment of acute intoxications between 1970 and 1980. Life-threatening valproic acid toxicity is an indication for coated charcoal hemoperfusion usually accomplished without complications, but we report a case of acute severe intravascular hemolysis during the time of hemoperfusion with coated charcoal column.