A suite of robust controllers for the manipulation of microscale objects.

A suite of novel robust controllers is introduced for the pickup operation of microscale objects in a microelectromechanical system (MEMS). In MEMS, adhesive, surface tension, friction, and van der Waals forces are dominant. Moreover, these forces are typically unknown. The proposed robust controller overcomes the unknown contact dynamics and ensures its performance in the presence of actuator constraints by assuming that the upper bounds on these forces are known. On the other hand, for the robust adaptive critic-based neural network (NN) controller, the unknown dynamic forces are estimated online. It consists of an action NN for compensating the unknown system dynamics and a critic NN for approximating a certain strategic utility function and tuning the action NN weights. By using the Lyapunov approach, the uniform ultimate boundedness of the closed-loop manipulation error is shown for all the controllers for the pickup task. To imitate a practical system, a few system states are considered to be unavailable due to the presence of measurement noise. An output feedback version of the adaptive NN controller is proposed by exploiting the separation principle through a high-gain observer design. The problem of measurement noise is also overcome by constructing a reference system. Simulation results are presented and compared to substantiate the theoretical conclusions.     

Fabrication and integration of microscale permanent magnets for particle separation in microfluidics

Microfluidic magnetophoresis is an effective technique to separate magnetically labeled bioconjugates in lab-on-a-chip applications. However, it is challenging and expensive to fabricate and integrate microscale permanent magnets into microfluidic devices with conventional methods that use thin-film deposition and lithography. Here, we propose and demonstrate a simple and low-cost technique to fabricate microscale permanent magnetic microstructures and integrate them into microfluidic devices. In this method, microstructure channels were fabricated next to a microfluidic channel and were injected with a liquid mixture of neodymium (NdFeB) powders and polydimethylsiloxane (PDMS). After the mixture was cured, the resulted solid NdFeB–PDMS microstructure was permanently magnetized to form microscale magnets. The microscale magnets generate strong magnetic forces capable of separating magnetic particles in microfluidic channels. Systematic experiments and numerical simulations were conducted to study the geometric effects of the microscale magnets. It was found that rectangular microscale magnets generate larger \(({\mathbf {H}}\cdot \nabla ) {\mathbf {H}}\) which is proportional to magnetic force and have a wider range of influence than the semicircle or triangle magnets. For multiple connected rectangular microscale magnet, additional geometric parameters, including separation distance, height and width of the individual elements, further influence the particle separation and were characterized experimentally. With an optimal size combination, complete separation of yeast cells and magnetic microparticles of similar sizes (\(4\;\upmu \hbox {m}\)) was demonstrated with the multi-rectangular magnet microfluidic device.     

A numerical study of the Coriolis effect in centrifugal microfluidics with different channel arrangements

The Coriolis force has been of great interest to control the transversal flow that is critical for mixing or switching fluids in centrifugal microfluidics. Therefore, the variation in the Coriolis effect has been extensively investigated by varying the rotational speeds and the cross-sectional geometry of microchannels. However, the subject of such investigations has been limited to radially positioned microchannels even though channels can lie everywhere on the rotating platform with different arrangements. In this study, we use numerical methods to investigate the Coriolis effect resulting from the angular alignment (AA) and radial displacement (RD) of rotating microchannels. Our analysis focuses on determining the contribution that different channel arrangements have in the deviation of parabolic velocity profiles, which is generally produced by the effective Coriolis force. We found that the flow can deviate even at a low rotational speed, where the Coriolis force is negligible, with an AA of up to 33 % which is a sufficient amount for flow switching. Once the rotational speed reaches to the critical RPM, the flow deviates by an effective Coriolis force, but the deviation systematically varies with AA or RD. As the Coriolis force becomes more dominant with a high rotational speed, the deviation reaches a saturation point, while flow rate is regulated by AA or RD, enabling the flow rate to remain low even at very high RPM, without reducing the deviation. The variation in the Coriolis effect due to the different channel arrangements investigated in this study is believed to provide an essential basis to design and develop centrifugal microfluidic systems.     

Control of secondary flow in concentrically traveling flow on centrifugal microfluidics

This paper reports a fundamental study of the stripe laminar flow pattern on a centrifugal microfluidic device with the goal of realizing a sedimentation-based, continuous mode particle separation technique. Microfluidic channels were designed with a concentrically integrated microchannel, and the patterning of the flow in the channel was investigated. A significant secondary flow was observed as a preliminary result. We conclude that the origin of this secondary flow was not the Dean force, because it was observed in a straight microchannel, but was not observed in curved channel during the spinning of the system at rest. The transition of the pattern was investigated using a simulation and experiment, and the flow pattern’s dependence on the rotational speed was determined, which suggested that the origin of the secondary flow was the Coriolis force. The significance of the secondary flow was controlled by adjusting the rotational speed of the disk, and the flow rate and laminar flow patterns were controlled by the stripe flow pattern.     

Wandering: A Web-based platform for the creation of location-based interactive learning objects

Wandering is an innovative web-based platform that was designed to facilitate outdoor, authentic, and interactive learning via the creation of location-based interactive learning objects (LILOs). Wandering was integrated as part of a novel environmental education program among middle school students. This paper describes the Wandering platform's structural architecture and an evaluation study that was conducted among grade nine students (N = 102) who participated in the innovative educational program. Our goal was to examine students' learning outcomes and experiences while creating LILOs' and providing comments. Findings indicated high motivation among students to use Wandering, not only for completing their school assignment, but also for contributing to the community. Despite the fact that the tagging and commenting tools could have been used more efficiently by students, more than one third of the LILOs received an excellent grad. In addition, our findings indicated that Wandering is a good platform for enhancing 21st century skills, including: engagement with others, personalization, control release, and change adaption.     

细纱机始纺位置信号采集系统研究

利用霍尔传感器设计了一种全新的细纱机始纺信号采集装置。经实验证明，与以前的行程开关始纺位置信号采集装置相比，使用该结构的细纱机始纺位置信号采集装置具有易调整、性能稳定、使用寿命长的优点，同时加工容易，制造成本低且便于推广。     

A new approach on indexing mobile objects on the plane

We present a set of time-efficient approaches to index objects moving on the plane to efficiently answer range queries about their future positions. Our algorithms are based on previously described solutions as well as on the employment of efficient access methods. Finally, an experimental evaluation is included that shows the performance, scalability and efficiency of our methods.     

基于多传感器融合的运动平台运动目标检测

基于运动平台的运动目标检测在计算机视觉等领域有着十分广阔的应用,基于单一视觉传感器平台目前很难满足实用要求。提出一种融合视觉传感器、微机电惯性传感器和距离传感器信息的运动平台运动目标检测新方法。利用惯性传感器获得的平台运动信息和距离传感器获得的场景深度信息,采用由粗到精的图像配准策略,消除背景运动影响。利用配准后的图像信息在扩展卡尔曼滤波框架下对惯性传感器信息进行修正,以达到长期稳定检测的目的。实验结果证明了方法的稳健性和有效性。     

A new technique for the determination of gases in metals

A new technique for the determination of gases in metals using a vacuum spark is described. It is relatively simple and fast in comparison with known methods. Its application to determine gases in aluminum wire is presented. A sensitive way to determine the thickness of metal coatings or to study diffusion processes is suggested.     

Driving and sorting of the fluorescent droplets on digital microfluidic platform

In this paper, we present a digital microfluidic droplet sorting platform to achieve automated droplet sorting based on fluorescent detection. We design and fabricate a kind of digital microfluidic chip for manipulating nano-liter-sized liquid droplets, and the chip is integrated with a fluorescence-initiated feedback system for real-time sorting control. The driving and sorting characteristics of fluorescent droplets encapsulating fluorescent-labeled particles are studied on this platform. The droplets dispensed from on-chip reservoir electrode are transported to a fluorescence detection site and sorted according to their fluorescence signals. The fluorescent droplets and non-fluorescent droplets are successfully separated and the number of fluorescent particles inside each droplet is quantified by its fluorescent intensity. We realize droplet sorting at 20 Hz and obtain a linear relationship between the fluorescent particle concentrations and the fluorescence signals. This work is easily adapted for sorting out fluorescent-labeled microparticles, cells and bacteria and thus has the potential of quantifying catalytic or regulatory bio-activities.     

A new method for representing and matching shapes of natural objects

A new method for the representation and comparison of irregular two-dimensional shapes is presented. This method uses a polar transformation of the contour points about the geometric centre of the object. The distinctive vertices of the shape are extracted and used as comparative parameters to minimize the difference of contour distance from the centre. Experiments are performed, more than 39 000 comparisons of database shapes, provided by Sebastian et al. (ICCV (2001) 755), are made and the results are compared to those obtained therein. In addition, 450 comparisons of leaf shape are made and leaves of very similar shape are accurately distinguished. The method is shown to be invariant to translation, rotation and scaling and highly accurate in shape distinction. The method shows more tolerance to scale variation than that of Sebastian et al. (ICCV (2001) 755) and is less computationally intense.     

A new technique for the solution of the Saha equation

A new computational technique for solving the Saha equation, which calculates the ionization states of gases, is presented. The algorithm is safe, converges quickly and is simple to implement. Pseudocode of the program is given to assist such implementation. Accuracy checks are described. Limitations of the technique at high ionization are discussed.     

A polymeric micro-optical system for the spatial monitoring in two-phase microfluidics

This article presents a polymeric micro-optical system that consists of two coupled miniaturized devices for spatially distributed characterization of microfluidic two-phase phenomena exploiting multiwavelength optical signals. The input device implements four optical windows (slits) which are superimposed on the centerline of a microfluidic serpentine channel and illuminate specific locations of the microchannel. The flow-related information is then collected by an ad hoc polymeric micro-optical output device that guides and merges the spatially distributed information into a single output signal, which maintains memory of the spatial coordinates by using the wavelengths as fingerprints of the slits’ position in the microfluidic channel. Both micro-optical devices were designed, simulated, and characterized in static and dynamic conditions. Experiments on two-phase (air and ethanol) flow were carried out by applying constant and periodic flow rate functions. In both cases, the system was proved to be efficient in capturing the spatial–temporal dynamics of flow profiles.     

A new technique for measuring the mechanical properties of thinfilms

Accurate measurement of mechanical properties is very difficult for films that are only a few microns thick. Previously, these properties have been determined by indirect methods such as cantilever beam and diaphragm bulge tests. This paper presents a new technique to measure the Young's modulus of thin films in a direct manner consistent with its definition. Strain is measured by a laser-based technique that enables direct and accurate recording of strain on a thin-film specimen. Load is recorded with a 1-lb load cell, and an air bearing is used to eliminate friction in the loading system. The specimen is phosphorus-doped polysilicon that has a gage cross section of 3.5 μm thick by 600 μm wide. All 29 uniaxial tensile tests show brittle behavior, and the average values of Young's modulus and fracture strength are measured to be 170±6.7 GPa and 1.21±0.16 GPa, respectively. One fatigue test is also reported in this paper     

基于双循环测量隔离管路的离心泵加速寿命试验平台设计

针对离心泵失效过程复杂、故障数据库不健全的问题,设计了基于双循环测量隔离管路的离心泵加速寿命试验平台。该平台利用含砂粒子大小与粒子浓度作为离心泵加速寿命应力因子,以流量-扬程特性曲线作为寿命评价指标。测试结果表明,该平台可以有效加速离心泵失效过程,并能实现离心泵特性曲线拟合和试验数据的在线测量,满足了加速寿命试验要求。     

A new lossless orthogonal simplification method for 3D objects based on bounding structures

This paper presents a new approach to simplify 3D binary images and general orthogonal pseudo-polyhedra (OPP). The method is incremental and produces a level-of-detail sequence of OPP, where any object of this sequence bounds the previous objects and, therefore, is a bounding orthogonal approximation of them. The sequence finishes with the axis-aligned bounding box. OPP are encoded using the Extreme Vertices Model, a complete model that stores a subset of their vertices and performs fast Boolean operations. Simplification is achieved by using a new strategy, which relies on the application of 2D Boolean operations. We also present a technique, based on model continuity, for better shape preservation. Finally, we present a data structure to encode in a progressive and lossless way the generated sequence. Tests with several datasets show that the proposed method produces smaller storage sizes and good quality approximations compared with other methods that also produce bounding objects.     

A new reduction technique for a class of singularly perturbedoptimal control problems

We consider a class of singularly perturbed optimal control problems which may not be approximated by the reduced problems constructed via the formal replacement of the fast variables by the states of equilibrium of the “fast” subsystem considered with “frozen” slow variables and controls. We construct a reduced optimal control problem which provides a true approximation for the problems under consideration and write down the necessary and sufficient optimality conditions for this reduced problem     

Development of a new spinning gait for a planar snake robot using central pattern generators

In this paper, we first present dynamic equation of n-link snake robot using Lagrange’s method in a simplified matrix form and verify them experimentally. Next, we introduce a new locomotion mode called spinning gait. Central pattern generators (CPGs) are used for online gait generation. To realize spinning gait, genetic algorithm is used to find optimal CPG network parameters. We illustrate both theoretically, using derived robot dynamics and experimentally that the CPG-based online gait generation method allows continuous and rather smooth transitions between gaits. Lastly, we present an application where the snake robot is guided from an initial to final position while avoiding obstacles by changing CPG parameters.     

A FORTRAN V program for a new classification technique: the g-mode central method

The G-mode central method is described. This method allows a large number of samples to be classified based on several variables. The classification method works without a priori knowledge of the taxonomic homogeneous units forming the statistical sample.