An intelligent system for sorting pistachio nut varieties

An intelligent pistachio nut sorting system combining acoustic emissions analysis, Principal Component Analysis (PCA) and Multilayer Feedforward Neural Network (MFNN) classifier was developed and tested. To evaluate the performance of the system 3200 pistachio nuts from four native Iranian pistachio nut varieties were used. Each variety was consisted of 400 split-shells and 400 closed-shells nut. The nuts were randomly selected, slide down a chute, inclined 60° above the horizontal, on which nuts slide down to impact a steel plate and their acoustic signals were recorded from the impact. Sound signals in the time-domain are saved for subsequent analysis. The method is based on feature generation by Fast Fourier Transform (FFT), feature reduction by PCA and classification by MFNN. Features such as amplitude, phase and power spectrum of sound signals are computed via a 1024-point FFT. By using PCA more than 98% reduction in the dimension of feature vector is achieved. To find the optimal MFNN classifier, various topologies each having different number of neurons in the hidden layer were designed and evaluated. The best MFNN model had a 40–12–4 structure, that is, a network having one hidden layer with 40 neurons at its input, 12 neurons in the hidden layer and 4 neurons (pistachio varieties) in the output layer. The selection of the optimal model was based on the examination of mean square error, correlation coefficient and correct separation rate (CSR). The CSR or total weighted average in system accuracy for the 40–12–4 structure was 97.5%, that is, only 2.5% of nuts were misclassified.     

Laser beam soldering – a new assembly technology for microoptical systems

Based on the development of an adhering and solderable layer system microoptical subsystems are joined by laser beam soldering. Fluxless processing with AuSn – solder (80/20 weight%) results in joints that are stable, leak-proof and that contain low mechanical stress. REM – investigations show that the joining area is homogenous. The paper will discuss a number of industrial applications.The work was partially supported by the German government in a BMBF / VDI-VDE project (Microoptical modules for the modular MST – MOBMO, Project Nr. 16SV2147) and by the Thuringian government (Soldering of microoptical and optoelectronical components – LOMO, Project Nr. 105023).     

Comparative study of analytical and numerical algorithms for designing reinforced concrete sections under biaxial bending

This paper presents a comparative study of different integration methods of stresses (both analytical and numerical) for concrete sections subjected to axial loads and biaxial bending. Such methods are applied to circular and rectangular sections. The constitutive equation used is a parabola-rectangle from the Eurocode-2. The comparison was performed with regard to the accuracy and the computational speed of each method. The objective of the paper is to determine which of the integration methods compared is more efficient in computing the interaction surfaces for rectangular and circular sections. The analytical method proposed by Barros et al. [Barros MHFM, Barros A, Ferreira C. Closed form solution of optimal design of rectangular reinforced concrete sections. Eng Comput 2004;21(7):761–76] for rectangular sections is compared with the numerical method termed “modified thick layer integration” proposed by Bonet et al. [Bonet JL, Romero ML, Miguel PF, Fernandez MA. A fast stress integration algorithm for reinforced concrete sections with axial loads and biaxial bending. Comput Struct 2004;82(2–3):213–25] and with the well-known fiber method. Furthermore, two new methods are proposed for circular sections: one analytical and one numerical based on the Gauss–Legendre quadrature. The results of both methods are compared with the classical layer decomposition method.     

On the impact of the synchronization constraint and interconnections in quantum-dot cellular automata

Quantum-dot Cellular Automata (QCA) is an emerging nanotechnology with remarkable performance and energy efficiency. Computation and information transfer in QCA are based on field forces rather than electric currents. As a consequence, new strategies are required for design automation approaches in order to cope with the arising challenges. One of these challenges is the transport of information, which is affected by two particularities of the QCA technology. First, information flow in QCA is controlled by external clocks, and second, QCA is a planar technology in which gates, as well as interconnections, are mostly located in the same layer. The former demands proper synchronization already during the circuit design phase, while the latter results in high area costs for interconnections. This work focuses on both constraints and discusses its impact on the implementation of QCA circuits. Further, the concept of local and global synchronicity in QCA circuits is explored. The obtained results indicate that relaxing the global synchronicity constraint can reduce design size by about 70% while the throughput performance declines by similar values. Additionally, it can be shown that the impact of interconnections in QCA, like wires, fan-outs, and crossovers, is indeed substantial. That means, up to 75% of the total area is occupied by interconnections.     

Improvements in graphite-based X-ray mask fabrication for ultradeep X-ray lithography

Hard x-ray masks for ultradeep x-ray lithography (UDXRL) at synchrotron radiation sources, such as the Advanced Photon Source, require a gold absorber thickness of 20–100 m on a low-Z substrate, such as silicon, graphite, or beryllium. Graphite sheets of 0.5 mm were used for the fabrication of x-ray masks by standard optical lithography using a SU-8 photoresist. The conductivity of graphite is sufficient to perform electroplating directly without the need for a metal-plating base layer. Gold electroforming was used to deposit a 85-m-thick patterned absorber layer. The masks were used for UDXRL using hard x-rays at the Advanced Photon Source.This work has been supported by the U.S. Department of Energy, Office of Science, under Contract No. W-31–109-ENG-38, by AFOSR Grant 49620–00–1-0088, and by DUSD (S&T) under the Innovative Microwave Vacuum Electronics MURI program managed by the AFOSR under grant F49620–99–1-0297.     

Hierarchical channel router

The channel routing problem is a special case of the wire routing problem when interconnections have to be performed within a rectangular strip having no obstructions between terminals located on opposite sides of the rectangle.We present here a new channel routing algorithm, based on reduction of the problem to the case of a ($\text{2 × n}$) grid and on consistent utilization of a ‘divide-and-conquer’ approach. For the current implementation of the algorithm, the running time is proportional to $\text{N}{}^1\text{n}\text{log}\text{(m)}$ where $\text{N}$ is the number of nets, $\text{n}$ the length of the channel (number of columns) and $\text{m}$ the width of the channel (number of tracks).Traditional technological restrictions are assumed, ie, net terminals are located on vertical grid lines, two wiring layers are available for interconnections. One layer is used exclusively for vertical segments and another for horizontal. Vias are introduced for each layer change.This algorithm consistently outperforms several known routers in quality of wiring. We tested the algorithm on several benchmark problems. One of them, Deutsch's ‘difficult example’, was routed with only 19 horizontal wiring tracks (the absolute minimum for this case), whereas all other known routers required 20 or more tracks.     

Speed–accuracy tradeoff in Fitts’ law tasks—on the equivalency of actual and nominal pointing precision

Pointing tasks in human–computer interaction obey certain speed–accuracy tradeoff rules. In general, the more accurate the task to be accomplished, the longer it takes and vice versa. Fitts’ law models the speed–accuracy tradeoff effect in pointing as imposed by the task parameters, through Fitts’ index of difficulty (I_d) based on the ratio of the nominal movement distance and the size of the target. Operating with different speed or accuracy biases, performers may utilize more or less area than the target specifies, introducing another subjective layer of speed–accuracy tradeoff relative to the task specification. A conventional approach to overcome the impact of the subjective layer of speed–accuracy tradeoff is to use the a posteriori “effective” pointing precision W_e in lieu of the nominal target width W. Such an approach has lacked a theoretical or empirical foundation. This study investigates the nature and the relationship of the two layers of speed–accuracy tradeoff by systematically controlling both I_d and the index of target utilization I_u in a set of four experiments. Their results show that the impacts of the two layers of speed–accuracy tradeoff are not fundamentally equivalent. The use of W_e could indeed compensate for the difference in target utilization, but not completely. More logical Fitts’ law parameter estimates can be obtained by the W_e adjustment, although its use also lowers the correlation between pointing time and the index of difficulty. The study also shows the complex interaction effect between I_d and I_u, suggesting that a simple and complete model accommodating both layers of speed–accuracy tradeoff may not exist.     

A combinative technique to fabricate hot embossing master for PMMA tunneling sensors

A combinative approach of anisotropic bulk etching and modified plasma etching has been successfully employed in a single wafer to fabricate silicon masters for the hot embossing process. The masters hold both pyramid pits and positive profile sidewalls with smooth surfaces and steep angles. The SiO₂ layer is utilized as a etching mask with the aid of photoresist in three steps of photolithography patterning. The first polymethyl-methacrylate (PMMA)-based tunneling transducer with polymer membrane structures is fabricated by hot embossing replication with the silicon master. Consequently, the exponential relations between tunneling currents and applied deflection voltages are also reported.This work is partially supported by grants NSF/LEQSF (2001–04)-RII-02, DARPA DAAD19–02–1-0338, and NASA (2002)-Stennis-22.     

Neural-Network-Based Decentralized Adaptive Control for a Class of Large-Scale Nonlinear Systems With Unknown Time-Varying Delays

A decentralized adaptive methodology is presented for large-scale nonlinear systems with model uncertainties and time-delayed interconnections unmatched in control inputs. The interaction terms with unknown time-varying delays are bounded by unknown nonlinear bounding functions related to all states and are compensated by choosing appropriate Lyapunov–Krasovskii functionals and using the function approximation technique based on neural networks. The proposed memoryless local controller for each subsystem can simply be designed by extending the dynamic surface design technique to nonlinear systems with time-varying delayed interconnections. In addition, we prove that all the signals in the closed-loop system are semiglobally uniformly bounded, and the control errors converge to an adjustable neighborhood of the origin. Finally, an example is provided to illustrate the effectiveness of the proposed control system.      

High density and through wafer copper interconnections and solder bumps for MEMS wafer-level packaging

This paper proposes an innovative process combining the electroforming of high-density and through-wafer copper interconnections and solder bumps for advanced MEMS packaging. Vias with the diameter of 30 to 100 m were etched through on a 4-inch and 550 m-thick silicon substrate by ICP-DRIE process for an aspect ratio up to 18.3. MRTV1 silicon rubber layer was employed for substrates quickly releasing after copper-interconnections electroforming. Compared to the tedious wet etching or mechanical polishing process, this peel-off relasing process provides a simpler way. After another lithography process, mushroom shape eutecic solder bumps (63Sn/37Pb) were directly electroformed on the top of each copper interconnection with the height of 100 m, and reflowed at 200 °C for 5 min to form solder spheres. The feasibility of making highly dense and uniform electrical interconncetions has been successfully demonstrated on the wafer with fabricated micro temperature sensors. The estimated resistance for the copper-column of different diameters are characterized lower than 13.1 m and this process provides a bump density up to 9648 interconnects/cm².This paper was partially supported by the contract NSC 89–2323-B-007–005, through National Science Council, Taiwan. We also appreciate the help from MicroSystem Common Laboratory at Industrial Technology Research Institute for ICP-DRIE process.     

Attenuating Artificial Dissipation in the Computation of Navier–Stokes Turbulent Boundary Layers

We propose a new formulation of the fourth-difference artificial dissipation coefficient needed for the Navier–Stokes solutions. This coefficient is scaled by a damping function which is expressed in terms of the Baldwin–Lomax algebraic turbulence model. The suggested scaling function damps the artificial dissipation across the boundary layer. The objective of this paper is to test the ability of the suggested damped scaling coefficient to provide (a) a given accuracy on a coarser grid; and (b) an accurate computing of turbulent boundary layers. To accomplish this, attached and separated transonic flows over the NACA 0012 airfoil, and turbulent flow over a flat plate have been considered.     

Characterization of a multi-chip microelectrofluidic bench for modular fluidic and electric interconnections

We present the design, fabrication, and characterization of a multi-chip microelectrofluidic bench, achieving both fluidic and electric interconnections with simple and low pressure-loss interconnections. The microelectrofluidic bench provides easy alignment of fluidic interconnection using microfabricated annular fluidic connectors; also provides simple electric interconnection using isotropic conductive adhesives at room temperature. Thus, the present microelectrofluidic bench provides a modular concept for fluidic and electric interconnection. In experimental study, we characterize pressure losses, electric resistances loss, and pressure stability of the interconnection. The average pressure drop per each fluidic contact is measured 0.12 ± 0.19 kPa at the DI water flow rate from 10 to 100 μl min⁻¹. The electric resistance per each electric contact is measured as 0.64 ± 0.29 Ω. The fluidic interconnection endures maximum pressure of 115 ± 11 kPa. The present microelectrofluidic bench, therefore, offers a simple and low pressure-loss electrofluidic modular interconnection for electrofluidic multi-chip microsystems.     

Electrical and photoelectrical characterizations of isotype GaAs15P85/GaP heterojunctions prepared by liquid phase epitaxy

The present work deals with the electrical and optoelectronic characterizations of the isotype GaAs₁₅P₈₅/GaP devices prepared by liquid phase epitaxy. The electrical properties of the fabricated junction were studied by analyzing its current–voltage (I–V) characteristics, capacitance–voltage (C–V) characteristics in the dark at different temperatures in the range of 300–450 K. The analysis of dark current–voltage (I–V) characteristics at different temperatures were presented in order to elucidate the conduction mechanism and to evaluate the important device parameters. The predominant charge transport mechanism in these devices was found to be thermionic emission in the depletion layer and over the barrier of GaAs₁₅P₈₅/GaP heterojunction at forward bias voltage. From the capacitance–voltage, measurements at high frequency (1 MHz) information can be obtained about the carrier concentration, the diffusion potential, the barrier height of GaAs₁₅P₈₅/GaP heterojunction. The current–voltage characteristics of the GaAs₁₅P₈₅/GaP heterojunction under different illumination intensities were studied. The power low dependence of the reverse current voltage is characterized by space charge limited conduction, SCLC dominated by exponential trap distribution at the higher reverse voltage region.     

Vapour sensing with conductive polymer nanocomposites (CPC): Polycarbonate-carbon nanotubes transducers with hierarchical structure processed by spray layer by layer

The development of conductive polymer nanocomposite (CPC) sensors for volatile organic compounds (VOC) detection has been carried out using a spray layer by layer (LbL) process. This technique was successfully used to hierarchically structure polycarbonate-multiwall carbon nanotubes (PC-CNT) solutions into a double percolated architecture as attested by atomic force microscopy (AFM) and optical microscopy (OM). PC-CNT vapour sensing behaviour was investigated as a function of CNT content, films thickness, vapour flow and vapours solubility parameter. The response ranking A_r(toluene) > A_r(methanol) > A_r(water) of PC-CNT was found to be coherent with κ₁₂ Flory–Huggins interaction parameters provided that signals are normalised by analyte molecules number. Signals shape was interpreted to the light of Langmuir–Henry–Clustering (LHC) model and found to be proportional to vapour content.     

A large-displacement 65Pb(Mg1/3Nb2/3)O3–35PbTiO3/Pt bimorph actuator prepared by screen printing

In this paper we present a novel approach to preparing large-displacement 65Pb(Mg_1/3Nb_2/3)O₃–35PbTiO₃/Pt (65/35 PMN–PT/Pt) bimorph actuators. These “substrate-free”, bending-type actuators were prepared by screen-printing the 65/35 PMN–PT and Pt thick-film pastes as the electrodes on alumina substrates. After this screen printing and the subsequent firing the 65/35 PMN–PT/Pt composites were peeled off from the substrates. Displacements of nearly 100 μm at 18 V were achieved for actuators with dimensions of 1.8 cm × 2.5 mm × 50 μm for the 65/35 PMN–PT layer. The normalized displacement (the displacement per unit length) was 40 μm/cm at 18 V. The experimental results together with a computation procedure were used to obtain the material parameters for a finite-element analysis of the 65/35 PMN–PT/Pt bimorph actuators.     

Piezoelectric linear motor with unimorph structure by co-extrusion process

A new piezoelectric linear motor was developed using a ring-shaped, unimorph stator composed of a piezoelectric active layer (0.3PZN–0.7PZT/Mn) and a conductive passive layer (0.3PZN–0.7PZT/Mn/Ag). The stator was prepared by co-extrusion followed by the thermoplastic green machining (TGM) process. After co-extruding the piezoelectrically active and passive layers together, they were machined into a ring shape and then sintered at 930 °C for 4 h. The stator was poled in the thickness direction and operated in radial vibration mode. A glass rod was used as the moving shaft. When a saw-tooth electric field was applied, the shaft moved linearly as a result of the stator's bending motion. When an inverted saw-tooth electric potential was applied, the shaft moved linearly in the opposite direction. The velocity of the piezoelectric linear motor was about 4 mm/s at an applied voltage of 80 V_p–p and a resonance frequency of 36.5 kHz.     

A graph-to-layout correspondence in single layer routing

A new method of attacking the hierarchically decomposed single layer routing problem is proposed.A placement is used to orient the initial graph structure. Such a structure becomes an encoded picture of future interconnections. The router is capable of decoding it to produce a blocking-free wiring pattern.     

Zeolite cover layer for selectivity enhancement of p-type semiconducting hydrocarbon sensors

Screen-printed thick films of the p-type semiconducting materials family SrTi_1−xFe_xO_3−δ have been investigated for hydrocarbon sensing. Among the different compositions tested, the formulations containing 10 and 20% of iron are found to perform best for this purpose. A pronounced cross-interference of NO persisted at operating temperatures of about 400 °C. In order to eliminate this problem, the application of a zeolite cover layer was studied. The properties of this cover layer were optimized with respect to layer thickness and Pt content. Using initial results of a catalytic study on the zeolite powder in addition to a simple diffusion–reaction model, the effect of the zeolite layer with respect to NO cross-interference could be explained satisfactorily.     

Unexpected vertical profiles over complex terrain due to the incomplete formulation of transport processes in the SAIMM/UAM-V air quality model

The air quality model (AQM) package SAIMM/UAM-V Systems Applications International Mesoscale Model/Urban Airshed Model with Variable grid was applied to a domain with complex topography including Switzerland. The output pressure at a fixed height above sea level generated by one of the SAIMM post-processor showed unexpected variations of about 40 hPa over the domain. We found that these fluctuations were caused by an incorrect definition of the pressure reference height. After the change of this definition, realistic pressure values were obtained. Using the correct pressure field as input, we simulated the 3-dimensional mixing ratios of pollutants with UAM-V for the summer smog period of July 28–29, 1993. The values tended to increase with height above the surface and with surface elevation above sea level. The Swiss topography was mirrored in the mixing ratio fields. By using CO as a quasi-inert tracer, it became evident that transport phenomena such as advection and diffusion did not consider expansions or compressions due to pressure and temperature variations. After the conversion of the concentrations to a common reference pressure and temperature before the calculation of transport, these strange topographic features in the mixing ratios vanished completely. The CO mixing ratio was underestimated by 10–15 ppb (7–10%) in the lowest layer over the Swiss Plateau due the omission of compression or expansion. For O₃ and NO₂, the differences were 0–5 ppb (0–10%) and 0–0.2 ppb (0–15%), respectively.