Integrating intuitive and novel grounded concepts in a dynamic geometry learning environment

The development of geometry knowledge requires integration of intuitive and novel concepts. While instruction may take many representational forms we argue that grounding novel information in perception and action systems in the context of challenging activities will promote deeper learning. To facilitate learning we introduce a grounded integration pattern of instruction, focusing on (1) eliciting intuitive concepts, (2) introducing novel grounding metaphors, and (3) embedding challenges to promote distinguishing between ideas. To investigate this pattern we compared elementary school children in two conditions who engaged in variations of a computer-based dynamic geometry learning environment that was intended to elicit intuitive concepts of shapes. In the grounded integration condition children performed a procedure of explicitly identifying defining features of shapes (e.g. right angles) with the assistance of animated depictions of spatially-meaningful gestures (e.g. hands forming right angles). In a numerical integration condition children identified defining features with the assistance of a numerical representation. Children in the grounded integration were more likely to accurately identify target shapes in a posttest identification task. We discuss the relevancy of the grounded integration pattern on the development of instructional tools.     

Why Taddeo and Floridi did not solve the symbol grounding problem

The symbol grounding problem (SGP), which remains difficult for AI and philosophy of information, was recently scrutinised by Taddeo and Floridi (Solving the symbol grounding problem: A critical review of fifteen years of research. Journal of Experimental & Theoretical Artificial Intelligence, 17, 419–445, 2005; A praxical solution of the symbol grounding problem. Minds and machines, 17, 369–389, doi:10.1007/s11023-007-9081-32005, 2007). However, their own solution to SGP, underwritten by Action-based Semantics, although different from other solutions, does not seem to be satisfactory. Moreover, it does not satisfy the authors' principle, which they dub ‘Zero Semantic Commitment Condition’. In this paper, Taddeo and Floridi's solution is criticised in particular because of the excessively liberal relationship between symbols and internal states of agents, which is conceived in terms of levels of abstraction. Also, the notion of action seems to be seriously defective in their theory. Due to the lack of the possibility of symbols to misrepresent, the grounded symbols remain useless for the cognitive system itself, and it is unclear why they should be grounded in the first place, as the role of grounded symbols is not specified by the proposed solution. At the same time, it is probably one of the best-developed attempts to solve SGP and shows that naturalised semantics can benefit from taking artificial intelligence seriously.     

Effects of dynamic contact angle on numerical modeling of electrowetting in parallel plate microchannels

Electrowetting phenomenon in parallel plate microchannel is investigated numerically. The current study advances accuracy of numerical modeling of electrowetting by considering dynamic behavior of the tri-phase contact line using molecular-kinetic theory. This theory in conjunction with volume of fluid method, which has been proved to be a powerful approach for free surface modeling, is used to simulate the phenomenon. By comparing the results against experimental data from literature, the simulation demonstrates significant improvement in results. It is concluded that ignoring dynamic features of wetting leads to overestimation of the effect of electrowetting actuation on various parameters including contact angle, aspect ratio and velocity of the droplet.     

Electrokinetic motion of an electrically induced Janus droplet in microchannels

The electrokinetic motion of an electrically induced Janus oil droplet with one side covered with an aluminum oxide nanoparticle film in a circular microchannel was numerically simulated in this paper. The Janus oil droplet is electrically anisotropic as the nanoparticle-covered area carries positive charges and the rest oil–water surface area carries negative charges. A theoretical model was constructed to calculate the electrokinetic velocity of the Janus droplet by considering the force balance on the surface of the Janus droplet at steady state. In the model, the effects of the electric double layer and surface charges on the motion at the oil–water interface are considered. The effects of five parameters on the electrokinetic motion of the Janus droplets were studied: the electric field, the zeta potential ratio of the positively charged side to the negatively charged side of the Janus droplet, the viscosity ratio of the oil phase to the water phase, the nanoparticle coverage of the Janus droplet, and the size ratio of the diameter of the Janus droplet to the diameter of the cylindrical microchannel. The simulation results indicate that the increase in the electrical field, the zeta potential ratio, the viscosity ratio or the nanoparticle coverage leads to faster electrokinetic motion of the Janus droplet. On the other hand, with the increase in size ratio, the electrokinetic velocity of Janus droplet first decreases gradually then increases sharply. The simulated results were compared with the experimental results and good agreement was found.     

Driving characteristics of the electrowetting-on-dielectric device using atomic-layer-deposited aluminum oxide as the dielectric

Electrowetting on dielectric (EWOD) is useful in manipulating droplets for digital (droplet-based) microfluidics, but its high driving voltage over several tens of volts has been a barrier to overcome. This article presents the characteristics of EWOD device with aluminum oxide (Al₂O₃, ε _r  ≈ 10) deposited by atomic layer deposition (ALD), for the first time as the high-k dielectric for lowering the EWOD driving voltage substantially. The EWOD device of the single-plate configuration was fabricated by several steps for the control electrode array of 1 mm × 1 mm squares with 50 μm space, the dielectric layer of 1,270 Å thick ALD Al₂O₃, the reference electrode of 20 μm wide line electrode, and the hydrophobic surface treatment by Teflon-AF coating, respectively. We observed the movement of a 2 μl water droplet in an air environment, applying a voltage between one of the control electrodes and the reference electrode in contact with the droplet. The droplet velocity exponentially depending on the applied voltage below 15 V was obtained. The measured threshold voltage to move the droplet was as low as 3 V which is the lowest voltage reported so far in the EWOD researches. This result opens a possibility of manipulating droplets, without any surfactant or oil treatment, at only a few volts by EWOD using ALD Al₂O₃ as the dielectric.     

Droplet generation in micro-sieve dispersion device

Microfluidic devices with micro-sieve plate as the dispersion medium have been widely used for the mass production of emulsions. While unfortunately, few studies have so far been made for the droplet generation rules in those devices. In this work, the droplet generation processes in micro-sieve dispersion devices are investigated with specially designed micro-sieve pore arrays. The effects of channel structure, pore arrangement, and feeding method of dispersed phase on the average size and distribution of droplets are studied carefully. It is found the dimensionless average droplet diameters (d _av/d _e) in micro-sieve dispersion devices can be represented by a linear relation with Ca^−1/4 of continuous phase, the same as the scaling law in T-junction microchannels. The flow distribution among pores and the steric hindrance between droplets affect the diameter distribution of generated droplet very much. Monodispersed droplets with polydispersity index less than 5% can be made at Ca number larger than 0.01 and phase ratio (Q _D/Q _C) less than 1/6 in the present investigation.     

Pumping of electrolytes using travelling-wave electro-osmosis: a weakly nonlinear analysis

The interaction between ac electric fields and the induced charge in the double layer formed on top of electrodes generates steady motion of aqueous solutions. This phenomenon is termed ac electro-osmosis. Unidirectional fluid motion is obtained when the electrolyte is placed on top of an array of microelectrodes subjected to a travelling-wave potential. In this work, we analyse the generated fluid motion assuming that the electrodes are perfectly polarisable and making use of the nonlinear Gouy–Chapman model for the diffuse double layer. We approximate the applied potential at the level of the electrodes by a single-mode travelling wave. We present numerical and analytical solutions obtained in the weakly nonlinear regime and the results are discussed and related with previous experimental observations.

Droplet transport through dielectrophoretic actuation using line electrode

We explore a novel transverse line electrode configuration for droplet transport through dielectrophoretic actuation with potential lab-on-chip applications. Using a lumped electromechanical model, we show a weak dependence of DEP actuation force on electrode spacing in this configuration. The configuration successfully triggers translational drop motion with minimal changes in contact angle at considerably low voltages. Two sessile, deionized water drops placed horizontally apart on a indium-tin–oxide-coated glass with additional coatings of polydimethylsiloxane, and a thin layer of Teflon is merged by applying an AC field (88 V_rms at 150 kHz) through a common horizontal wire electrode. A lateral motion of two drops is induced along the horizontal electrode, eventually leading to coalescence. The drop motion is unique compared to electrowetting in its near-constant dynamic contact angle, and irreversibility on withdrawal of electric field. The effect of frequency on the drop behavior is examined through a parametric study on single drops within the range of 2–200 kHz. It is interesting to observe a switch-over from DEP behavior at high frequency to EWOD behavior at low frequency around a critical frequency (Jones in Langmuir 18:4437–4443, 2002).     

The design of autonomous DNA nano-mechanical devices: Walking and rolling DNA

We provide designs for the first autonomousDNA nanomechanical devices that execute cycles of motion without external environmental changes. These DNA devices translate along a circular strand of ssDNA and rotate simultaneously. The designs use various energy sources to fuel the movements, include (i) ATP consumption by DNA ligase in conjunction with restriction enzyme operations, (ii) DNA hybridization energy in trapped states, and (iii) kinetic (heat) energy. We show that each of these energy sources can be used to fuel random bidirectional movements that acquire after n steps an expected translational deviation of O(√n). For the devices using the first two fuel sources, the rate of stepping is accelerated over the rate of random drift due to kinetic (heat) energy. Our first DNA device, which we call walking DNA, achieves random bidirectional motion around a circular ssDNA strand by use of DNA ligase and two restriction enzymes. Our other DNA device, which we call rolling DNA, achieves random bidirectional motion without use of DNA ligase or any restriction enzyme, and instead using hybridization energy. We also describe how to modify the design for the rolling DNA device to include a ``latching mechanism' that fixes the wheels position at specified location along the road, so as to provide for overall unidirectional translational movement. This revised version was published online in June 2006 with corrections to the Cover Date.     

基于物联网数据采集的携带型短路接地线监测系统研究

短路接地线是保证电力生产人身安全的重要设备。传统携带型短路接地线,缺乏智能化的监测手段,常出现漏挂、错挂、漏拆等情况,给人身、设备以及电网安全带来安全隐患甚至发生人身伤亡事故。本文基于物联网技术,设计包括感知层、网络层、平台层和应用层的总体框架,研发接地线智能监测装置与系统,实现对接地线分布、挂接状态、设备信息等的自动采集、移动实时监测和综合管理。通过在国网无锡供电公司实际场景试点,证明该智能监测装置和系统能够直观展现接地设备多维度信息,且具有实时性、移动性和扩展性特点,有效辅助安全管理决策,提升现场安全综合管控水平。     

A scaling model for electrowetting-on-dielectric microfluidic actuators

A hydrodynamic scaling model of droplet actuation in an electrowetting-on-dielectric (EWD) actuator is presented that takes into account the effects of contact angle hysteresis, drag from the filler fluid, drag from the solid walls, and change in the actuation force while a droplet traverses a neighboring electrode. Based on this model, the threshold voltage, V _T, for droplet actuation is estimated as a function of the filler medium of a scaled device. It is shown that scaling models of droplet splitting and liquid dispensing all show a similar scaling dependence on [t/ε_r(d/L)]^1/2, where t is insulator thickness and d/L is the aspect ratio of the device. It is also determined that reliable operation of a EWD actuator is possible as long as the device is operated within the limits of the Lippmann–Young equation. The upper limit on applied voltage, V _sat, corresponds to contact-angle saturation. The minimum 3-electrode splitting voltages as a function of aspect ratio d/L < 1 for an oil medium are less than V _sat. However, for an air medium the minimum voltage for 3-electrode droplet splitting exceeds V _sat for d/L ≥ 0.4. EWD actuators were fabricated to operate with droplets down to 35pl. Reasonable scaling results were achieved.

Characteristics and impact of <Emphasis Type="Italic">Taq</Emphasis> enzyme adsorption on surfaces in microfluidic devices

We investigated the adsorption of Taq enzyme, using sessile droplets, on different microfluidic materials. In propagating adsorption materials, the contact angle (CA) of a sessile Taq droplet continually recedes and collapses due to adsorption. Contrastingly, in contained adsorption materials it exhibits an initial reduced CA due to an instantaneous adsorption, however remains time-invariant. Spectrophotometer analysis on SU8, a propagating adsorption material, reveals a gradual loss of Taq from the droplet onto the surface during droplet collapsing, as opposed to a rapid saturated adsorption in Teflon, a contained adsorption material. AFM micrographs of the adsorbed surfaces suggest a network-like structure in SU8 and distinctly different pillar-like structures in Teflon. With this understanding, we have successfully applied a SU8-Teflon coating to impart a time-invariant contact angle with minimal loss of Taq in surface microfluidic devices.     

Molecular simulations of droplet evaporation by heat transfer

Droplet evaporation by heat transfer is investigated by molecular dynamics simulations for a pure Lennard-Jones fluid. Two different initial conditions are treated: (1) a droplet surrounded by its vapor in equilibrium, (2) a cold droplet surrounded by warm vapor. In both cases heat is transferred from a heat bath. Results are the numbers of droplet molecules N _d and density, drift velocity, and temperature profiles as functions of time. For the small droplets considered N _d depends on the definition of a droplet molecule. The density profiles as function of time show a transition from a droplet with liquid–vapor interface to a cluster of interfacial type and finally to the gas state. The temperature at a given time is nearly constant within the droplets or clusters but strong gradients occur in the gas. In case of evaporation of a cold droplet surrounded by warm vapor we observed initially cooling down of the droplet corresponding to pressure jump evaporation and thereafter slower evaporation because of lower initial state vapor density.     

Camera Motion Estimation Through Planar Deformation Determination

In this paper, we propose a global method for estimating the motion of a camera which films a static scene. Our approach is direct, fast and robust, and deals with adjacent frames of a sequence. It is based on a quadratic approximation of the deformation between two images, in the case of a scene with constant depth in the camera coordinate system. This condition is very restrictive but we show that, provided translation and depth inverse variations are small enough, the error on optical flow involved by the approximation of depths by a constant is small. In this context, we propose a new model of camera motion which allows to separate the image deformation in a similarity and a “purely” projective application, due to change of optical axis direction. This model leads to a quadratic approximation of image deformation that we estimate with an M-estimator; we can immediately deduce camera motion parameters. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.

基于EWOD的锥形管状结构液体变焦透镜

提出了一种基于介质上电润湿(EWOD)的液体变焦透镜的新结构.它由一个依次覆盖有ITO透明导电薄膜及疏水介质膜的下极板、悬在其上的一个内外壁均覆盖有疏水层的玻璃锥管以及处于两者之间的导电液滴组成.通过改变ITO与液滴之间的电压大小,透镜的曲率及位置能同时被调节,从而实现对透镜焦距的调节.实验结果表明,该器件在0～50 V电压下可实现对2 cm至无穷远处物体的聚焦.     

运动特征激励的无候选框视频描述定位

目的 视频描述定位是视频理解领域一个重要且具有挑战性的任务,该任务需要根据一个自然语言描述的查询,从一段未修剪的视频中定位出文本描述的视频片段。由于语言模态与视频模态之间存在巨大的特征表示差异,因此如何构建出合适的视频—文本多模态特征表示,并准确高效地定位目标片段成为该任务的关键点和难点。针对上述问题,本文聚焦于构建视频—文本多模态特征的优化表示,提出使用视频中的运动信息去激励多模态特征表示中的运动语义信息,并以无候选框的方式实现视频描述定位。方法 基于自注意力的方法提取自然语言描述中的多个短语特征,并与视频特征进行跨模态融合,得到多个关注不同语义短语的多模态特征。为了优化多模态特征表示,分别从时序维度及特征通道两个方面进行建模： 1）在时序维度上使用跳连卷积,即一维时序卷积对运动信息的局部上下文进行建模,在时序维度上对齐语义短语与视频片段; 2）在特征通道上使用运动激励,通过计算时序相邻的多模态特征向量之间的差异,构建出响应运动信息的通道权重分布,从而激励多模态特征中表示运动信息的通道。本文关注不同语义短语的多模态特征融合,采用非局部神经网络（non-local neural network）建模不同语义短语之间的依赖关系,并采用时序注意力池化模块将多模态特征融合为一个特征向量,回归得到目标片段的开始与结束时刻。结果 在多个数据集上验证了本文方法的有效性。在Charades-STA数据集和ActivityNet Captions数据集上,模型的平均交并比（mean intersection over union,mIoU）分别达到了52.36%和42.97%,模型在两个数据集上的召回率R@1 （Recall@1）分别在交并比阈值为0.3、0.5和0.7时达到了73.79%、61.16%和52.36%以及60.54%、43.68%和25.43%。与LGI （local-global video-text interactions）和CPNet （contextual pyramid network）等方法相比,本文方法在性能上均有明显的提升。结论 本文在视频描述定位任务上提出了使用运动特征激励优化视频—文本多模态特征表示的方法,在多个数据集上的实验结果证明了运动激励下的特征能够更好地表征视频片段和语言查询的匹配信息。     

A microtranslation table with scratch-drive actuators fabricated from silicon-on-insulator wafer

From a silicon-on-insulator (SOI) wafer, a microtranslation table with scratch-drive actuator (SDA) has been fabricated. The device Si layer of SOI wafer is etched to form the plate of SDA, which is partially connected to the handle Si substrate by the SiO₂ layer. Dicing the handle Si substrate, a microtranslation table with the SDA array has been fabricated. Placing the microtranslation table upside down on the other Si substrate on which a thin conductive film is patterned for the electrical connection, the microtranslation table is moved by the SDA without carrying a metal wire. The moving velocity of 45.5 μm/s has been obtained by applying the voltage of 120 V at the operating frequency of 500 Hz.     

Flexible Splicing of Upper‐Body Motion Spaces on Locomotion

This paper presents an efficient technique for synthesizing motions by stitching, or splicing, an upper‐body motion retrieved from a motion space on top of an existing lower‐body locomotion of another motion. Compared to the standard motion splicing problem, motion space splicing imposes new challenges as both the upper and lower body motions might not be known in advance. Our technique is the first motion (space) splicing technique that propagates temporal and spatial properties of the lower‐body locomotion to the newly generated upper‐body motion and vice versa. Whereas existing techniques only adapt the upper‐body motion to fit the lower‐body motion, our technique also adapts the lower‐body locomotion based on the upper body task for a more coherent full‐body motion. In this paper, we will show that our decoupled approach is able to generate high‐fidelity full‐body motion for interactive applications such as games.