新型开关稳压电源的优化设计与应用

针对小功率开关电源所普遍存在的问题,实现了一种新型小功率高频开关稳压电源的优化设计。本文采用Power Integrations公司推出的TOP244Y单片开关电源芯片,设计与制作了应用于变频器的辅助开关电源。实际应用结果充分体现了该开关电源体积小、可靠性高、稳压性能好等优势。     

Geometrical optimization of microstripe arrays for microbead magnetophoresis

Manipulation of magnetic beads plays an increasingly important role in molecular diagnostics. Magnetophoresis is a promising technique for selective transportation of magnetic beads in lab-on-a-chip systems. We investigate periodic arrays of exchange-biased permalloy microstripes fabricated using a single lithography step. Magnetic beads can be continuously moved across such arrays by combining the spatially periodic magnetic field from microstripes with a rotating external magnetic field. By measuring and modeling the magnetophoresis properties of thirteen different stripe designs, we study the effect of the stripe geometry on the magnetophoretic transport properties of the magnetic microbeads between the stripes. We show that a symmetric geometry with equal width of and spacing between the microstripes facilitates faster transportation and that the optimal period of the periodic stripe array is approximately three times the height of the bead center over the microstripes.     

初中数学函数建模活动的教学设计

中学数学建模是在教师的引导下,学生遵循数学建模的典型环节,综合运用数学知识、自主研究解决实际问题的实践活动。本文以家用汽车的经济时速问题为例,对初中数学函数建模活动进行了教学设计。     

H2 and H∞ optimal model reduction using genetic algorithms

The mathematical modeling of most physical systems, such as aerospace systems, heat processes, telecommunication systems, transmission lines and chemical reactors, results in complex high order models. The complexity of the models imposes a lot of difficulties in analysis, simulation and control designs. Several analytical model reduction techniques have been proposed in literature over the past few decades to reduce these difficulties. However, most of the optimal techniques follow computationally demanding, time consuming, iterative procedures that usually result in non-robustly stable models with poor frequency response resemblance to the original high order model in some frequency ranges. Genetic Algorithm (GA) has proved to be an excellent optimization tool in the past few years. Therefore, the aim of this paper will be to use GA to solve H₂ and H_∞ norm model reduction problems, and help obtain globally optimized nominal models.     

总量控制下的地方政府公共就业规模优化分配研究——基于地方政府竞合视角

分析了公共就业规模优化分配与地方政府职能转变的适应性关系及各地方政府在公共就业规模优化分配中的博弈行为,设计了基于效率和讨价还价博弈的公共就业规模优化分配模型。实际应用表明,此优化分配模型具有一定的可行性和合理性。     

Tuning bubbly structures in microchannels

Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row ("dripping"), to multiple rows ("alternating"), to densely packed bubbles ("bamboo" and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters.     

Multi-objective optimal design of inerter-based vibration absorbers for earthquake protection of multi-storey building structures

In recent years different inerter-based vibration absorbers (IVAs) emerged for the earthquake protection of building structures coupling viscous and tuned-mass dampers with an inerter device. In the three most popular IVAs the inerter is functioning either as a motion amplifier [tuned-viscous-mass-damper (TVMD) configuration], mass amplifier [tuned-mass-damper-inerter (TMDI) configuration], or mass substitute [tuned-inerter-damper (TID) configuration]. Previous work has shown that through proper tuning, IVAs achieve enhanced earthquake-induced vibration suppression and/or weight reduction compared to conventional dampers/absorbers, but at the expense of increased control forces exerted from the IVA to the host building structure. These potentially large forces are typically not accounted for by current IVA tuning approaches. In this regard, a multi-objective IVA design approach is herein developed to identify the compromise between the competing objectives of (i) suppressing earthquake-induced vibrations in buildings, and (ii) avoiding development of excessive IVA (control) forces, while, simultaneously, assessing the appropriateness of different modeling assumptions for practical design of IVAs for earthquake engineering applications. The potential of the approach to pinpoint Pareto optimal IVA designs against the above objectives is illustrated for different IVA placements along the height of a benchmark 9-storey steel frame structure. Objective (i) is quantified according to current performance-based seismic design trends using first-passage reliability criteria associated with the probability of exceeding pre-specified thresholds of storey drifts and/or floor accelerations being the engineering demand parameters (EDPs) of interest. A variant, simpler, formulation is also considered using as performance quantification the sum of EDP variances in accordance to traditional tuning methods for dynamic vibration absorbers. Objective (ii) is quantified through the variance of the IVA force. It is found that reduction of IVA control force of up to 3 times can be achieved with insignificant deterioration of building performance compared to the extreme Pareto optimal IVA design targeting maximum vibration suppression, while TID and TMDI achieve practically the same building performance and significantly outperform the TVMD. Moreover, it is shown that the simpler variant formulation may provide significantly suboptimal reliability performance. Lastly, it is verified that the efficacy of optimal IVA designs for stationary conditions is maintained for non-stationary stochastic excitation model capturing typical evolutionary features of earthquake excitations.     

Facile fabrication processes for hydrogel-based microfluidic devices made of natural biopolymers

We present facile strategies for the fabrication of two types of microfluidic devices made of hydrogels using the natural biopolymers, alginate, and gelatin as substrates. The processes presented include the molding-based preparation of hydrogel plates and their chemical bonding. To prepare calcium-alginate hydrogel microdevices, we suppressed the volume shrinkage of the alginate solution during gelation using propylene glycol alginate in the precursor solution along with sodium alginate. In addition, a chemical bonding method was developed using a polyelectrolyte membrane of poly-L-lysine as the electrostatic glue. To prepare gelatin-based microdevices, we used microbial transglutaminase to bond hydrogel plates chemically and to cross-link and stabilize the hydrogel matrix. As an application, mammalian cells (fibroblasts and vascular endothelial cells) were cultivated on the microchannel surface to form three-dimensional capillary-embedding tissue models for biological research and tissue engineering.     

学术会议论文新颖性测度研究——以计算机学科人工智能领域为例

【目的/意义】研究学术会议论文新颖性测度方法,为会议论文的新颖性评价提供新的视角。【方法/过程】本 文设计吸收新颖性指标和产出新颖性指标测度方法,选择“人工智能”领域的会议论文进行实证研究。【结果/结论】 具有高吸收新颖性水平和高产出新颖性水平的论文成为A类会议论文的几率最高,结果表明新颖性测度方法的有 效性,对于会议论文的自动评审有一定的参考意义。【创新/局限】设计会议论文新颖性测度方法,促进会议论文评 价的发展;只针对计算机的人工智能领域进行实证,具有一定的领域局限性。     

模块化组织核心企业模式及组织运行机制研究

从宏观层面角度,对模块化组织中"强势"和"弱势"核心企业模式的形成和角色进行了分析;在对模块化组织的组织设计、价值创新机制形成、组织治理模式等进行构建的基础上,进一步对组织的制度、结构、流程以及治理模式进行了设计,以更好地发挥模块化组织"协同"作用。     

考虑制造企业参与的合作服务创新契约研究

运用委托代理理论,以服务商的服务创新努力投入水平最大化为目标,设计考虑制造企业参与的特殊合作服务创新契约并分析其性质。研究结果表明:服务创新最优契约的存在以制造企业服务创新预算足够大为前提,且最优契约条款随着预算增大而增加,服务商保留收益增大倒逼制造企业增大服务创新预算;制造企业参与投入对服务商的服务创新最优努力投入水平产生正向影响,服务创新固定支付对最优服务创新条款产生负向影响;服务商的最优服务创新努力投入水平与服务创新的价值系数及其分享服务创新产出份额正相关,与其投入成本系数及制造企业参与努力成本系数均负相关,与外生随机变量对服务创新产出的影响系数正相关。     

A microdevice for the creation of patent, three-dimensional endothelial cell-based microcirculatory networks

Microvascular network formation is a significant and challenging goal in the engineering of large three-dimensional artificial tissue structures. We show here the development of a fully patent, 3D endothelial cell (microvascular) microfluidic network that has a single inlet and outlet, created in only 28 h in a microdevice involving fluid flow equivalent to natural vasculature. Our microdevice features a tailored "multi-rung ladder" network, a stylized mimic of an arterial-to-venous pedicle, designed to also allow for systematic and reproducible cell seeding. Immunofluorescence staining revealed a highly contiguous endothelial monolayer (human umbilical vein endothelial cells) throughout the whole network after 24 h of continuous perfusion. This network persisted for up to 72 h of culture, providing a useful template from which the effects of surface chemistry, fluid flow, and environmental conditions on the development of artificial vascular networks ex vivo may be rapidly and robustly evaluated.     

思政融入“电工电子学”课程的研究和探索

针对电工电子学课程的教学特点和教学内容,设计和改进教学方法和手段,将思政元素有机地融入每堂课的教学,探索了该课程与思政教育的结合方式,挖掘本课程能够结合“思政”的切入点和教育资源,建立了全过程、全方位、有案例的“课程思政”体系。教学实践证明这些改革和探索达到了较好的教学效果。     

Exploitation of physical and chemical constraints for three-dimensional microtissue construction in microfluidics

There are a plethora of approaches to construct microtissues as building blocks for the repair and regeneration of larger and complex tissues. Here we focus on various physical and chemical trapping methods for engineering three-dimensional microtissue constructs in microfluidic systems that recapitulate the in vivo tissue microstructures and functions. Advances in these in vitro tissue models have enabled various applications, including drug screening, disease or injury models, and cell-based biosensors. The future would see strides toward the mesoscale control of even finer tissue microstructures and the scaling of various designs for high throughput applications. These tools and knowledge will establish the foundation for precision engineering of complex tissues of the internal organs for biomedical applications.     

知识转化视角下民营企业新产品开发集成创新优化机制研究

新产品开发是中国民营企业的一项战略性目标。在知识经济时代,知识转化为新产品开发赋予的内在的动力。集成创新是中国民营企业新产品开发的主要形式。基于我国民营企业的样本数据,借助结构方程模型,经验性地研究解析民营企业知识转化、集成创新、新产品开发之间的相关性,发现知识转化的优化路径,揭示集成创新的优化机理,提出民营企业新产品开发的改进策略。研究结论为中国民营企业新产品开发机制的完善提供现实性的理论借鉴。     

神经网络和预报集成的若干问题及其对策

本文评述了神经网络在气象应用中存在的问题、产生的原因和网络结构设计的原则及经验,并提出了构造伪样本来诊断模型可能存在问题的方法;简述了预报集成的原理和原则,提出了构造因子子集差异法生成预报个体,进行集成,来解决小样本和因子选取问题的方案。     

Microfluidic model of monocyte extravasation reveals the role of hemodynamics and subendothelial matrix mechanics in regulating endothelial integrity

Extravasation of circulating cells is an essential process that governs tissue inflammation and the body''s response to pathogenic infection. To initiate anti-inflammatory and phagocytic functions within tissues, immune cells must cross the vascular endothelial barrier from the vessel lumen to the subluminal extracellular matrix. In this work, we present a microfluidic approach that enables the recreation of a three-dimensional, perfused endothelial vessel formed by human endothelial cells embedded within a collagen-rich matrix. Monocytes are introduced into the vessel perfusate, and we investigate the role of luminal flow and collagen concentration on extravasation. In vessels conditioned with the flow, increased monocyte adhesion to the vascular wall was observed, though fewer monocytes extravasated to the collagen hydrogel. Our results suggest that the lower rates of extravasation are due to the increased vessel integrity and reduced permeability of the endothelial monolayer. We further demonstrate that vascular permeability is a function of collagen hydrogel mass concentration, with increased collagen concentrations leading to elevated vascular permeability and increased extravasation. Collectively, our results demonstrate that extravasation of monocytes is highly regulated by the structural integrity of the endothelial monolayer. The microfluidic approach developed here allows for the dissection of the relative contributions of these cues to further understand the key governing processes that regulate circulating cell extravasation and inflammation.     

产品伤害危机应对策略效果研究

通过实验研究,得出了最优应对策略。结果表明:(1)产品伤害危机类型对最优应对策略存在调节作用,在可辩解型中最优的是辩解策略,在不可辩解型中最优的是和解策略;(2)危机类型和企业声誉对应对策略具有调节作用。最后本文指出了研究局限。     

智能岩石力学的发展

智能岩石力学是为突破“数据有限”和“变形破坏机理理解不清”的“瓶颈”而提出的一个新的交叉学科分支 ,在岩石力学专家系统、非线性动力学模型、参数反演、本构模型识别、开挖过程全局优化、集成智能分析等研究方面已取得重要进展。指出多场耦合智能模型、多尺度模型、精细仿真、Internet模型、遥控试验系统、综合集成系统等研究是下一步的发展方向。变革思维方式 ,加强原始创新和破坏性创新 ,建立智能岩石力学分析平台是本学科发展的关键对策     

基于专家智慧的危机研讨可视化系统设计

综合集成研讨厅体现了"人机结合,以人为本"的思想,为企业危机判别提供了新思路。而综合集成研讨厅中的专家智慧展示的可视化可以提高研讨决策的效率。论文分析了基于专家智慧的危机研讨可视化系统的需求、业务流程、系统功能结构和关键技术。并以"国美控制权之争"给企业可能带来的危机进行系统仿真,实现了专家发言的关键词词间关系可视化、关键词与专家发言消息可视化、专家研讨的论点提取及其排序的可视化。