Direct pattern formation of bacterial cells using micro-droplets generated by electrohydrodynamic forces

Bacterial cells were patterned efficiently on a nutrient-coated membrane in a direct, rapid, and cost-effective manner using electro-hydrodynamically generated micro-droplets. By varying the viscosity and electrical conductivity of the bacterial printing solution, uniform droplets were obtained. Escherichia coli cells were directly printed onto a membrane filter, followed by overnight incubation on an agar plate which created line patterns of bacterial colonies with a width of approximately 160 μm. Optimization of the concentration of the chemical components [i.e. the ethylene glycol (EG), phosphate buffer (PB), and sodium chloride (NaCl)] in the processing bacterial solution allowed successful growth and patterning of the cells. The optimal conditions to achieve the most effective cell growth and patterning on these printed surfaces were an EG concentration of 40 vol% and a concentration as low as 10 mM of PB or NaCl in the printing solution. Cells passing through the electric nozzle during the printing process remained viable.     

Modelling of UAV formation flight using 3D potential field

In this paper, we present a solution for formation flight and formation reconfiguration of unmanned aerial vehicles (UAVs). Based on a virtual leader approach, combined with an extended local potential field, the method is universal applicable by driving the vehicle’s auto pilot. The solution is verified, using a group of UAVs based on a simplified small scale helicopter, which is simulated in MATLAB^TM/Simulink^TM. As necessary for helicopters, the potential field approach is realized in 3D including obstacle and collision avoidance. The collision avoidance strategy could be used separately for the sense and avoid problem.     

Refinement of generated fuzzy production rules by using a fuzzy neural network.

Fuzzy production rules (FPRs) have been used for years to capture and represent fuzzy, vague, imprecise and uncertain domain knowledge in many fuzzy systems. There have been a lot of researches on how to generate or obtain FPRs. There exist two methods to obtain FPRs. One is by painstakingly, repeatedly and time-consuming interviewing domain experts to extract the domain knowledge. The other is by using some machine learning techniques to generate and extract FPRs from some training samples. These extracted rules, however, are found to be nonoptimal and sometimes redundant. Furthermore, these generated rules suffer from the problem of low accuracy of classifying or recognizing unseen examples. The reasons for having these problems are 1) the FPRs generated are not powerful enough to represent the domain knowledge, 2) the techniques used to generate FPRs are pre-matured, ad-hoc or may not be suitable for the problem, and 3) further refinement of the extracted rules has not been done. In this paper we look into the solutions of the above problems by 1) enhancing the representation power of FPRs by including local and global weights, 2) developing a fuzzy neural network (FNN) with enhanced learning algorithm, and 3) using this FNN to refine the local and global weights of FPRs. By experimenting our method with some existing benchmark examples, the proposed method is found to have high accuracy in classifying unseen samples without increasing the number of the FPRs extracted and the time required to consult with domain experts is greatly reduced.     

Design and fabrication of an electrostatically suspended microgyroscope using UV-LIGA technology

A micromachined electrostatically suspended gyroscope, with a wheel-like rotor housed by top stator and bottom stator, using UV-LIGA microfabrication technology, was presented. The designed structure and basic operating principle of the gyroscope are described. The key steps in the fabrication process, such as wet etching of Pyrex glass pits for soldering, and integration of thick nickel structures by removal of SU-8 mold, were considered in detail and well solved. Cr/Pt/photoresist was used as etching mask and the etched pits, in depth of near 30 μm, with aspect ratio (depth to undercutting) of 0.75, were obtained. With metal foundations constructed for consolidation, successful integration of the nickel structures, in thickness of 200 μm, was achieved by successful removal of the SU-8 mold using oleum. After the two stators and the rotor were fabricated separately, they were assembled and soldering bonded to form axial and radial small gaps, hence, the initial prototype of the microgyroscope was realized. The key techniques described in this paper can be applied to fabrication of other micro devices. The metal foundation method, associated with removal of SU-8 mold by oleum, is expected to make SU-8 wider applications in making integrated microstructures with fabricated circuitry on the same chip.     

Adaptive control for a d.c. motor controlled by a group of amplidynes using bilinear models

This paper presents a method for the application of adaptive control to a d.c. motor coupled with a group of amplidynes. The overall process is modelled as a bilinear system since no voltage or current is held constant. Standard adaptive control techniques are applied to compensate for undesirable deviations of the process parameters from their nominal values.     

Towards a practical remote-sensing model of suspended sediment concentrations in turbid waters using MERIS measurements

A new empirical index, termed the normalized suspended sediment index (NSSI), is proposed to predict total suspended sediment (TSS) concentrations in inland turbid waters using Medium Resolution Imaging Spectrometer (MERIS) full-resolution (FR) 300 m data. The algorithm is based on the normalized difference between two MERIS spectral bands, 560 and 760 nm. NSSI shows its potential in application to our study region – Poyang Lake – the largest freshwater lake in China. An exponential function (R² = 0.90, p < 0.01) accurately explained the variance in the in situ data and showed better performance for the TSS range 10–524 mg l^?1. The algorithm was then validated with TSS estimates using an atmospheric-corrected MERIS FR image. The validation showed that the NSSI algorithm was a more robust TSS algorithm than the band-ratio algorithms. Findings of this research imply that NSSI can be successfully used on MERIS images to obtain TSS in Poyang Lake. This work provided a practical remote-sensing approach to estimate TSS in the optically and hydrologically complex Poyang Lake and the method can be easily extended to other similar waters.     

Experimental observations of bands of suspended colloidal particles subject to shear flow and steady electric field

Manipulating suspended colloidal particles flowing through a microchannel is of interest in microfluidics and nanotechnology. However, the flow itself can affect the dynamics of these suspended particles via wall-normal “lift” forces. The near-wall dynamics of particles suspended in shear flow and subject to a dc electric field was quantified in combined Poiseuille and EO flow through a?~?30 μm deep channel. When the two flows are in opposite directions, the particles are attracted to the wall. They then assemble into very high aspect ratio structures, or concentrated streamwise “bands,” above a minimum electric field magnitude, and, it appears, a minimum near-wall shear rate. These bands only exist over the few micrometers next to the wall and are roughly periodic in the cross-stream direction, although there are no external forces along this direction. Experimental observations and dimensional analysis of the time for the first band to form and the number of bands over a field of view of ~?200 μm are presented for dilute suspensions of polystyrene particles over a range of particle radii, concentrations, and zeta potentials. To our knowledge, there is no theoretical explanation for band assembly, but the results presented here demonstrate that it occurs over a wide range of different particle and flow parameters.     

Modeling and simulation of a suspended microchannel resonator nano-sensor

Microsystem Technologies - In this paper, dynamic behavior of a piezoelectric sensor based on the suspended microchannel resonator (SMR) was modelled and simulated. Dynamic behavior of SMR with...     

一种悬浮石墨烯压力传感器的制造与建模

提出了一种适用于纳机电系统(NEMS)的悬浮石墨烯压力传感器,并结合传统微机械加工工艺提出了压力传感器的制造过程。利用拉曼光谱表征了机械剥离法得到的不同厚度的石墨烯薄膜,验证了石墨烯"G"峰与"2D"峰的强度与薄膜厚度有关。基于薄膜膨胀试验方法,给出了悬浮于矩形、方形与圆形3种空腔的石墨烯薄膜的最大变形与压差的关系,并分别计算了3种形状下薄膜的压力灵敏度,可知矩形情况下单层石墨烯薄膜的压力灵敏度最大,当矩形宽度、方形边长或圆形直径越大,薄膜厚度越小时,压力灵敏度越高,计算表明:这种压力传感器具有高灵敏度。     

Detection of total suspended sediments in the North Sea using AVHRR and ship data

This study reports on a combined investigation between in situ measurements of total suspended sediments, collected by ship, and remotely sensed data provided by the Advanced Very High Resolution Radiometer (AVHRR) during the winter-summer period of 1989. It is meant to be a case study stating the problems inherent to coastal waters and proposing a methodology to understand them. Ship and satellite data are compared in order to detect suspended sediments in case 2 waters in the North Sea through a linear regression analysis. The results show a wide range of coefficient of determination (R²) values. The highest values correspond to summer dates, while the lowest belonged to the winter and spring period. It was found that for the summer dates the relatively still atmospheric and water conditions were suitable for comparison with satellite data providing good values of R². In winter and spring, unsettled sea water conditions complicated the comparison of the data. It can be concluded that the seasonal stratification of the water column during summer time allows a better correlation between in situ and remotely sensed data than the typically well-mixed waters during winter.     

Fabrication of micro-parts by high aspect ratio structuring and metal injection molding using the supercritical debinding method

 High aspect ratio micro-fabrication method using metal injection molding (MIM) is developed. In the MIM process, the powder is mixed with the binder and the mixture is injection molded. The binder is extracted from the molded parts using supercritical carbon dioxide, and the parts are sintered. Employing this process, micro-pattern which has aspect ratio more than 5 can be molded by stainless-steel powder. In this method, a micro-pattern made by laser ablation is used as a die. As compared with other micro-fabrication techniques, this method can utilize the molding die repeatedly. Consequently, the cost of production micro-parts can be decreased by this method in the actual production process.     

Equivalence between the descriptions of cosmological models using a spinor field and a perfect fluid

A possibility of simulating a perfect fluid using spinor fields with different nonlinearities is investigated. Exact cosmological solutions to Einstein’s equations with spinor fields are compared to the corresponding ones with perfect fluids.     

Defeaturing CAD models using a geometry-based size field and facet-based reduction operators

We propose a method to automatically defeature a CAD model by detecting irrelevant features using a geometry-based size field and a method to remove the irrelevant features via facet-based operations on a discrete representation. A discrete B-Rep model is first created by obtaining a faceted representation of the CAD entities. The candidate facet entities are then marked for reduction using a geometry-based size field. This is accomplished by estimating local mesh sizes based on geometric criteria. If the field value at a facet entity goes below a user-specified threshold value then it is identified as an irrelevant feature and is marked for reduction. The reduction of marked facet entities is performed using various facet operators. Care is taken to retain a valid geometry and topology of the discrete model throughout the procedure. The original model is not altered as the defeaturing is performed on a separate discrete model. Associativity between the entities of the discrete model and that of original CAD model is maintained in order to decode the attributes and boundary conditions applied on the original CAD entities onto the mesh via the entities of the discrete model. Example models are presented to illustrate the effectiveness of the proposed approach.     

Optic flow field segmentation and motion estimation using a robustgenetic partitioning algorithm

Optic flow motion analysis represents an important family of visual information processing techniques in computer vision. Segmenting an optic flow field into coherent motion groups and estimating each underlying motion is a very challenging task when the optic flow field is projected from a scene of several independently moving objects. The problem is further complicated if the optic flow data are noisy and partially incorrect. In this paper, the authors present a novel framework for determining such optic flow fields by combining the conventional robust estimation with a modified genetic algorithm. The baseline model used in the development is a linear optic flow motion algorithm due to its computational simplicity. The statistical properties of the generalized linear regression (GLR) model are thoroughly explored and the sensitivity of the motion estimates toward data noise is quantitatively established. Conventional robust estimators are then incorporated into the linear regression model to suppress a small percentage of gross data errors or outliers. However, segmenting an optic flow field consisting of a large portion of incorrect data or multiple motion groups requires a very high robustness that is unattainable by the conventional robust estimators. To solve this problem, the authors propose a genetic partitioning algorithm that elegantly combines the robust estimation with the genetic algorithm by a bridging genetic operator called self-adaptation     

Prediction of sound generated by a rod-airfoil configuration using EASM DES and the generalised Lighthill/FW-H analogy

Sound generated by an airfoil in the wake of a rod is predicted numerically by using a Detached-Eddy Simulation (DES) unsteady flow field and a Ffowcs Williams and Hawkings acoustic analogy formulation for the far field computation. Volume sources from the rod wake are found to play a non-negligible role at high frequencies and surface contributions might be flawed if the surfaces cross highly turbulent flow regions even if surrounding volume terms are accounted for. The DES approach is based on a novel cubic explicit algebraic stress turbulence model which is built on a two-equation k-ε model from Lien and Lechziner. This DES has been recently implemented at the Berlin University of Technology in the compressible Navier-Stokes flow solver ELAN. The aerodynamic results are compared to experimental data obtained at the ECL by Jacob et al., as well as to previous Large Eddy Simulations results from the Proust/Turbflow code by Boudet et al. and DES simulations from Greschner et al. based on standard turbulence models. The acoustic analogy is applied both with and without volume terms to rigid and permeable control surfaces surrounding the rod-airfoil system. Aeroacoustic results are compared to experimental data from the literature, showing that the inclusion of volume terms improves the aeroacoustic prediction in the broadband high frequency range.     

Sampling and analysis of particles generated in contact start/stop-mode of a hard disk drive by using a particle sampler

Particle contamination must be controlled to increase the storage capacity of a hard disk drive (HDD) as the flying height of the slider decreases. In the primary steps of particle contamination control, particles are precisely detected and analyzed. To carry out these steps, many researchers have used sampling methods. In this paper, we newly designed a particle sampler and evaluated the performance of the sampler. This sampler can collect particles by the applied electric field, by the impaction of particles, and by Brownian diffusion onto the sampling plate. We tested the performance of our sampler in terms of the parameters that affect the sampling efficiency of the particle sampler; sampling airflow rate, particle size, and externally applied electric field. The maximum sampling efficiency of unipolarly charged particles whose sizes ranged from 50 to 400 nm was about 90%. Also, we sampled particles generated during 20 contact start/stop cycles (CSS) of the HDD by using the particle sampler and analyzed the sampled particles by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The SEM images showed that the sizes of the particles decreased and the number of sampled particles increased as the disk rotational speed increased. The AES spectrum showed that the sampled particles were composed of P, C, Ni and Al, which are the components of the disk materials. Therefore, we believed that the generated particles originated from the disk surface. To determine the overall sampling efficiency of the particle sampler, particles generated in the HDD were counted at the inlet and outlet of the sampler. The overall sampling efficiency increased with increasing applied voltage and disk rotational speed. The maximum overall sampling efficiency of the particles generated in the HDD was about 70% when the applied voltage and disk rotational speed were 0.5 kV and 9,600 rpm, respectively.     

Quasi-static analysis of a.c. resistance of rectangular conductors

The distribution of current density over the cross section of a rectangular conductor is calculated by an integral equation method. The alternating current resistance is calculated from the current. The ac.c. resistance is needed in computation of the conductor losses in microstrip lines.     

干涉型光纤水听器相位载波解调技术

通过数学推导和仿真分析,对直接调制光源产生相位载波的马赫-曾德尔(Mach Zehnder)干涉型光纤水听器调制解调技术进行了研究。提出了不能通过干涉信号的峰值或峰峰值检测来控制自动增益控制(AGC)电路增益的方法消除偏振衰落对输出信号的影响。在这一思想的指导下完成了光纤水听器相位载波(PGC)解调电路的设计,给出了实验测试结果。