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.     

A new approach for the measurement of a.c. arc parameters using microprocessors

A microprocessor-based system was used to give true r.m.s. values of a.c. arc currents and voltages. With this approach more accurate results, compared with those obtained from classical instruments, were achieved.     

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.     

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.     

Wide field of view compressive light field display using a multilayer architecture and tracked viewers

In this paper, we discuss an intuitive extension to compressive multilayer light field displays that greatly extends their field of view and depth of field. Rather than optimizing these displays to create a moderately narrow field of view at the center of the display, we constrain optimization to create narrow view cones that are directed to a few viewers' eyes, allowing the available display bandwidth to be utilized more efficiently. These narrow view cones follow the viewers, creating a wide apparent field of view. Imagery is also recalculated for the viewers' exact eye positions, creating a greater depth of field. The view cones can be scaled to match the positional error and latency of the tracking system. Using more efficient optimization and commodity tracking hardware and software, we demonstrate a real‐time, glasses‐free 3D display that offers a 100° × 40° field of view.     

Autonomous recovery of a fixed‐wing UAV using a net suspended by two multirotor UAVs

This article presents a novel recovery method for fixed‐wing unmanned aerial vehicles (UAVs), aimed at enabling operations from marine vessels. Instead of using the conventional method of using a fixed net on the ship deck, we propose to suspend a net under two cooperative multirotor UAVs. While keeping their relative formation, the multirotor UAVs are able to intercept the incoming fixed‐wing UAV along a virtual runway over the sea and transport it back to the ship. In addition to discussing the concept and design a control system, this paper also presents experimental validation of the proposed concept for a small‐scale UAV platform.     

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.     

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。     

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...     

Cooperative localization and control of multiple heterogeneous robots using a string formation

This paper is on cooperative localization and control of multiple heterogeneous robots utilizing a string formation. This formation is preferred, since robots can move along a narrow passage utilizing this formation. Dead reckoning localization based on inertial measurement units leads to accumulated localization error. To avoid the error accumulation in dead reckoning localization, this paper introduces the last-move strategy for multiple heterogeneous robots. In the last-move strategy, a single robot is selected for maneuvering, and it turns on its bearing-range sensors for a short amount of time, in order to locate itself. While the selected robot moves, all other robots stop moving and perform as static landmarks for the moving robot. A robot may not maintain its desired course, in the case where environmental disturbance is severe. We thus develop a control strategy for avoiding obstacles while estimating the disturbance direction at a robot's location. To the best of our knowledge, this paper is novel in localization and control of a team of heterogeneous robots, considering the case where environmental disturbance is severe. The proposed localization process is energy-efficient, thus is suitable for practical applications. The performance of the proposed schemes is demonstrated utilizing MATLAB simulations.     

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.     

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.     

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.     

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.