Symmetric Orthogonal Complex-Valued Filter Bank Design by Semidefinite Programming

A new design method for complex-valued two-channel finite impulse response (FIR) filter banks with both orthogonality and symmetry properties is developed. Based on a novel linear matrix inequality (LMI) characterization of trigonometric curves, the optimal design of perfect-reconstruction filter banks is cast into a semidefinite programming (SDP) problem. The dimension of the resulting SDP problem is further reduced by exploiting convex duality. Consequently, the globally optimal solution can be found for any practical filter length and desired regularity order.     

Plasmon Resonances of Nanoshells of Spheroidal Shape

Plasmon resonances are computed for nanoshells of prolate and oblate spheroidal shape. Both longitudinal and transverse resonances are investigated as a function of aspect ratio and shell thickness. Formulas for the surface charge density on the outside and inside shell surfaces are derived.     

ADAPTIVE CONTROL DESIGN FOR NONLINEARLY PARAMETERIZED SYSTEMS WITH A TRIANGULAR STRUCTURE

A novel adaptive backstepping design for a class of nonlinearly parameterized systems with a triangular structure is proposed. Under the Lipschitz condition with respect to unknown parameters of the system, an effective adaptive controller is designed without the requirement on the compactness of the unknown parametric set. Especially, the proposed adaptive control enables the advantage of “tuning function concept”, which results in only one estimation law for the unknown parameters. Our simulation with induction motor model particularly shows the viability of the obtained results.     

D.C. optimization approach to robust control: Feasibility problems

The feasibility problem for constant scaling in output feedback control is considered. This is an inherently difficult problem since the set of feasible solutions is non-convex and may be disconnected. Nevertheless, we show that this problem can be reduced to the global minimization of a concave function over a convex set, or alternatively, to the global minimization of a convex program with an additional reverse convex constraint. Thus this feasibility problem belongs to the realm of d.c. optimization, a new field which has recently emerged as an active promising research direction in nonconvex global optimization. By exploiting the specific d.c. structure of the problem, several algorithms are proposed which at every iteration require solving only either convex or linear subproblems. Analogous algorithms with new characterizations are proposed for the bilinear matrix inequality (BMI) feasibility problem.     

Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules.     

泡沫基体电镀前处理工艺的改进

采用泡沫基体机构洗涤粗化、大批量敏化和低浓度钯离子（0.020-0.30g/L Pd^2 ）活化等工艺，对泡沫基体电镀前处理工艺进行了改进，泡沫粗化效果好，敏化用的SnCl2耗量仅为原工艺的1／5，钯的耗量为原来的1／3，泡沫基体的利用率由90％提高到98％，大大地提高泡沫镍产品的质量，大幅度地降低生成成本，取得了较好的经济效益。     

Reduction of charge injection into PECVD SiNxHy by control of deposition chemistry

The high rate of charge trapping in thin-film silicon nitride causes its electrical properties to change with stressing level and time. The rate of shift of the high-frequency CV curves of Al/SiN_xH_y/cSi capacitors was used here to measure nitride charging rate and to compare PECVD nitrides deposited under various conditions of plasma power and gas mixture in the same parallel-plate reactor. By operating the plasma under high power to activate the NH₃ or N₂ and under low SiH₄ flow to ensure that all of the SiH4 reacts with N, it is possible to deposit N-rich nitride that has no detectable Si—H bonding, which bonding others have correlated with charge trapping. Nitride deposited under these conditions using NH₃ and 13 MHz rf power had charging rates for both gate polarities that were 20 times lower than those of nitride that had a “stoichiometric” N/Si ratio of 4/3 and that had its H distributed among Si—H and N—H bonds. MIS capacitors made with the latter nitride also had a high negative initial flat-bond voltage, indicating the presence of grown-in positive charge. This charge was large enough to invert the surface ofp-Si substrates. N-rich nitride free of Si—H that was deposited either using N₂ or using low-frequency rf power (≤400 kHz) had higher charging rates than did that deposited from NH₃ at 13 MHz. Also, the low-frequency material contained grown-in positive charge that is attributed to H⁺ implanted by the high ion bombardment energy of the low-frequency plasma.     

Design of micro-electromagnetic drive on reciprocally rotating disc used for micro-gyroscopes

For micro-gyroscopes, the angular rate detection components have to oscillate forwards and backwards alternatively. An innovative design of micro-electromagnetic drive module is proposed to make a Π-type thin disc reciprocally and efficiently rotate within a certain of angular interval. Twelve EM (Electromagnetic) poles, with iron cores at the center and wound by electroplated copper wires, enclosing the thin disc are designed to provide the magnetic drive power. Isotropic etching technique is employed to fabricate the high-aspect-ratio trench, housing of the follow-up electroplated copper, so that the contact angle of wire against trench can be increased and the potential defect of cavities and pores within the wire can be prevented. On the other hand, a Π-type thin disc, with a central bearing and a set of auxiliary bushing, is designed to conduct the pitch motion as an angular excitation, in addition to spinning, is exerted on the gyroscope. That is, the angular motion of the disc is two-dimensional: spinning, driven by the EM poles, and tilting, to respond to the exerted angular rate due to Coriolis effect.The efficacy of the micro-magnetic drive module is verified by theoretical analysis and computer simulations by the commercial software, Ansoft Maxewll. In comparison with the conventional planar windings in micro-scale systems, the magnetic drive force is increased by 150%.