A detailed derivation of arrays free of higher rank ambiguities

Since linear dependence of steering vectors would lead to ambiguous direction-of-arrival (DOA) estimates, it is crucial to employ array with linearly independent steering vectors in DOA estimation applications. In fact, it is well known that in order to determine uniquely the DOAs of ν uncorrelated signals, one requires an array that is free of up to rank-ν ambiguities (i.e., an array whose every (ν+1) steering vectors with distinct DOAs are linearly independent). However, the question as to the sensor arrangement that gives rise to an array that is free of up to rank-ν ambiguities, where ν∈{3,...}, remains unanswered. We construct a class of cross arrays that are free of up to rank-ν ambiguities, where ν∈{1,...}. Through this study, we derive a theorem for characterizing inherent ambiguities associated with cross arrays. We also provide counterexamples to the conjecture for characterizing higher rank ambiguity proposed by Lo and Marple (see ibid., vol.40., p.2641-50, 1992) and that proposed by Wang et al. (see ICASSP'9, vol.IV, p.509-12, 1994)     

High-extinction ratio and low-loss silica-based 8×8thermooptic matrix switch

A high-extinction ratio and low-loss silica-based 8×8 thermooptic matrix switch is demonstrated. The 8×8 matrix switch is realized by using a double Mach-Zehnder interferometer switching unit and a matrix arrangement which reduces the total waveguide length. The average extinction ratio and the average insertion loss are 60.3 and 5.2 dB, respectively     

Fowler-Nordheim stress degradation in gate oxide: results fromgate-to-drain capacitance and charge pumping current

The buildup of positive oxide charge and interface trap charge, due to Fowler-Nordheim stress, is observed in the gate-drain overlap region of the MOSFET. Results from gate-to-drain capacitance and charge pumping current show a steady increase in positive charge near the anode interface. Interface trap generation becomes significant when injected electron fluence exceeds ~10¹⁴ cm^-2, and dominates net charge creation at higher fluence     

Cumulative probability control charts for geometric and exponential process characteristics

A statistical process control chart called the cumulative probability control chart (CPC-chart) is proposed. The CPC-chart is motivated from two existing statistical control charts, the cumulative count control chart (CCC-chart) and the cumulative quantity control chart (CQC-chart). The CCC- and CQC-charts are effective in monitoring production processes when the defect rate is low and the traditional p - and c -charts do not perform well. In a CPC-chart, the cumulative probability of the geometric or exponential random variable is plotted against the sample number, and hence the actual cumulative probability is indicated on the chart. Apart from maintaining all the favourable features of the CCC- and CQC-charts, the CPC-chart is more flexible and it can resolve a technical plotting inconvenience of the CCC- and CQC-charts.     

Sequential Data Fusion via Vector Spaces: Fusion of Heterogeneous Data in the Complex Domain

A sequential data fusion approach via higher dimensional vector spaces is introduced. This is achieved by making use of the representation of directional signals within the field of complex numbers . The concept of data fusion is next introduced and the place of the proposed approach within that framework is identified. The benefits of such an approach are illustrated and a range of possible applications is shown. The concept introduced is supported by a real world case study which focuses on simultaneous forecasting of wind speed and direction. The architectures and learning algorithms which support this concept are introduced and their distributed sequential fusion nature is highlighted.     

Low-power consumption silica-based 2×2 thermooptic switchusing trenched silicon substrate

We propose a silica-based 2×2 thermooptic switch using heat insulating grooves and trenches on a Si substrate to reduce electric power consumption. The switching power of a fabricated switch was successfully reduced to 135 mW, less than 1/3 that of a conventional switch. No detrimental effect on optical characteristics was observed: we obtained the insertion loss of 1 dB, the extinction ratio of better than 30 dB and no polarization dependency     

Hydrothermal preparation of high saturation magnetization and coercivity cobalt ferrite nanocrystals without subsequent calcination

In this work, CoFe₂O₄ nanocrystals with high saturation magnetization (M_s) and high coercivity (H_c) have been fabricated via a simple hydrothermal method and without subsequent calcination. The resulting CoFe₂O₄ nanocrystals are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, differential scanning calorimetry and vibrating sample magnetometry. The results indicate that CoFe₂O₄ nanocrystals are single crystal and the average crystallite size is increasing with the hydrothermal temperature. The electron micrographs show that the nanocrystals are well-dispersed and possess uniform size. The shape of CoFe₂O₄ nanocrystals is transformed from spherical into rod by increasing the hydrothermal temperature. The nanocrystals show relatively high M_s of 74.8 emu g⁻¹ and H_c of 2216 Oe, as compared to previous reported results. The obtained results reveal the applicability of this method for efficiently producing well crystallized and relatively high magnetic properties CoFe₂O₄ nanocrystals as compared to other methods. More importantly, it does not require further calcination processes.     

The pathway of development: science and technology of NIEs and selected Asian emerging economies

Many emerging countries in Asia demonstrate a strong pattern of growth and potential of diffusion in science and technology that is dynamic and self-propagating. To elucidate the evolution in science and technology and the institutional dynamics that drive the self-propagating behavior, this paper examines the divergent models pursued by selected Asian economies in regard to science and technological catch-up. An analysis of papers and patents production for each nation was conducted to examine the indigenous science and technology capabilities. This study focuses on six major economies, namely China, Malaysia, South Korea, Singapore, Taiwan and Thailand. In addition, Japan, a country with advanced development of science and technology, is included for comparison. The findings provided insight and understanding of evolving science and technological waves and the dynamic potentials in science and technology. We demonstrate the pursued catching-up models that drive the self-propagating behavior and industrialization, thus providing a more complete understanding of the innovation systems than those examined in previous studies.     

Determination of the Constitutive Constants of Non-Linear Viscoelastic Materials

A simple method for computing the strain and the time dependent constants for non-linear viscoelastic materials is presented. The method is based on the finite time increment formulation of the convolution integral, and is applicable for materials which exhibit separable strain and time variables. The strain-dependent function can take any form including the hyperelastic potentials such as the Mooney-Rivlin strain energy function. The time-dependent function is based on the Prony series. The attraction of the method is that true material constants can be computed for any deformation history.     

Fabrication and characterization of porous poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) scaffolds using solid–liquid phase separation

Freeze-extraction, which involves phase separation principle, gave highly porous scaffolds without the time and energy consuming freeze-drying process. The presented method eliminates the problem of formation of surface skin observed in freeze-drying methods. The effects of different freezing temperature (−80 and −24°C), medium (dry ice/ethanol bath and freezer) and polymer concentrations (1, 3, and 5 wt.%) on the scaffold properties were investigated in connection with the porous morphology and physicomechanical characteristics of the final scaffolds. The FESEM micrographs showed porous PLLA scaffolds with ladder-like architecture. The size of the longitudinal pores was in the range of 20–40 μm and the scaffolds had high porosity values ranging from 90% to 98%. Variation in porosity, mechanical resistance, and degree of regularity in the spatial organization of pores were observed when polymer concentration was changed. More open scaffold architecture with enhanced pore interconnectivity was achieved when a dry ice/ethanol bath of −80°C was used. Polymer concentration played an important role in fabricating highly porous scaffolds, with ladder-like architecture only appearing at polymer concentrations of above 3 wt.%. With the freeze-extraction method used here, highly porous and interconnected poly(l-lactide) scaffolds were successfully fabricated, holding great potential for tissue engineering applications.