利用电场感应器件MC33794测定液体高度

电场成像器件IC(MC33794)如今,设计工程师在需要非接触探测和三维(3D)电场成像的嵌入式系统中使用MC33794,可减少系统所需器件和成本。这款IC支持微控制器及多达9个简单的电极。这些电极均可独立使用,以提供在微弱电场中的物体尺寸和位置等信息。下文描述了利用此技术如何无干扰地测定液体高度。水的检测电场成像技术非常适合于非导电容器内液体高度的测定。测定工作可以在容器外完成,而且测量时无需内部或接地结构。这种方法可以测量任何介电常数的导电液体,或者介电常数比一般值大很多的非导电液体。水的测定可以通过放置于容器外的电…     

Profiling of micrometer-sized laser beams in restricted volumes

We present a method for determining the three-dimensional intensity distribution of directed laser radiation with micrometer resolution in restricted volumes. Our method is based on the incoupling and guiding properties of optical fibers, with the current version requiring only a few hundred micrometers across the measuring volume. We characterize the performance of the method and experimentally demonstrate profiling of micrometer-sized laser beams. We discuss the limiting factors and routes toward a further increase of the resolution and beam profiling in even more restricted volumes. Finally, as an application example, we present profiling of laser beams inside a micro ion trap with integrated optical fibers.     

Some aspects of the intraregional spatial distribution of local sector activities

This paper focuses on the spatial distribution of economic activities that serve the demands of households within a region. The level of local sector activities is measured by employment per inhabitant. The basic hypothesis relates to how this proportion varies systematically over space for a wide range of geographies, from high values in a city center to low values in areas adjacent to the city center, and asymptotically approaching the average regional level as the distance from the center increases. This defines a curve that we (under quite general conditions) find to be invariant under changes in the spatial residential pattern and the transportation structure. This suggests that relationships of this kind might be a powerful tool in the prediction of regional development.

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Mathematical analysis of oxygen transfer through polydimethylsiloxane membrane between double layers of cell culture channel and gas chamber in microfluidic oxygenator

For successful cell culture in microfluidic devices, precise control of the microenvironment, including gas transfer between the cells and the surrounding medium, is exceptionally important. The work is motivated by a polydimethylsiloxane (PDMS) microfluidic oxygenator chip for mammalian cell culture suggesting that the speed of the oxygen transfer may vary depending on the thickness of a PDMS membrane or the height of a fluid channel. In this paper, a model is presented to describe the oxygen transfer dynamics in the PDMS microfluidic oxygenator chip for mammalian cell culture. Theoretical studies were carried out to evaluate the oxygen profile within the multilayer device, consisting of a gas reservoir, a PDMS membrane, a fluid channel containing growth media, and a cell culture layer. The corresponding semi-analytical solution was derived to evaluate dissolved oxygen concentration within the heterogeneous materials, and was found to be in good agreement with the numerical solution. In addition, a separate analytical solution was obtained to investigate the oxygen pressure drop (OPD) along the cell layer due to oxygen uptake of cells, with experimental validation of the OPD model carried out using human umbilical vein endothelial cells cultured in a PDMS microfluidic oxygenator. Within the theoretical framework, the effects of several microfluidic oxygenator design parameters were studied, including cell type and critical device dimensions.     

An artefact suppressing fast-recovery myoelectric amplifier

An amplifier for recording myoelectric signals using surface electrodes has been developed. The special features are suppression of stimulation artefacts and motion artefacts from electrodes. It is designed for recording of myoelectric signals from a muscle that is being stimulated with short impulses. The artifact suppression is achieved by using fast-recovery instrumentation amplifiers and having a nonlinear feedback loop for automatic compensation of changes in DC-offset.     

Robust Optimization Model for a Dynamic Network Design Problem Under Demand Uncertainty

This paper describes a robust optimization approach for a network design problem explicitly incorporating traffic dynamics and demand uncertainty. In particular, we consider a cell transmission model based network design problem of the linear programming type and use box uncertainty sets to characterize the demand uncertainty. The major contribution of this paper is to formulate such a robust network design problem as a tractable linear programming model and demonstrate the model robustness by comparing its solution performance with the nominal solution from the corresponding deterministic model. The results of the numerical experiments justify the modeling advantage of the robust optimization approach and provide useful managerial insights for enacting capacity expansion policies under demand uncertainty.