Lifetime of excess electrons in Cu–Zn–Sn–Se powders

The method of time-resolved microwave photoconductivity at a frequency of 36 GHz in the range of temperatures of 200–300 K is used to study the kinetics of the annihilation of charge carriers in Cu–Zn–Sn–Se powders obtained by the solid-phase method of synthesis in cells. The lifetime of excess electrons at room temperature is found to be shorter than 5 ns. The activation energy for the process of recombination amounted to E _a ~ 0.054 eV.     

Compact microstrip dual-band bandpass filters design using genetic-algorithm techniques

An optimization scheme based on hybrid-coded genetic-algorithm (GA) techniques is presented to design compact dual-band bandpass filters with microstrip lines. A representation scheme is proposed to represent an arbitrary microstrip circuit as a set of data structures. Each data structure in the set describes a simple two-port network with the corresponding connection method and electrical parameters. The optimization algorithm based on conventional GAs is then applied to simultaneously search for the appropriate circuit topology and the corresponding electrical parameters with dual-band characteristic. Two examples are designed and implemented to validate the proposed algorithm. In the first example, the 3-dB fractional bandwidth of the low and high bands is 35% and 17%, respectively. It has return losses larger than 10 dB from 2.14 to 2.96 and 5.14 to 6.06 GHz. In the second example, the 3-dB fractional bandwidth of the low and high bands is 9.9% and 7.9%, respectively. The return losses are larger than 10 dB from 3.37 to 3.64 and 5.27 to 5.62 GHz. The sizes of the proposed filters are nearly half as small as those of the filters presented before. All the studies are completed on a computer with a 2.4-GHz microprocessor, and the computing time of two examples is 6 and 3 min, respectively.     

An optimal new-node placement to enhance the coverage of wireless sensor networks

Wireless sensor networks provide a wide range of applications, such as environment surveillance, hazard monitoring, traffic control, and other commercial or military applications. The quality of service provided by a sensor network relies on its coverage, i.e., how well an event can be tracked by sensors. This paper studies how to optimally deploy new sensors in order to improve the coverage of an existing network. The best- and worst-case coverage problems that are related to the observability of a path are addressed and formulated into computational geometry problems. We prove that there exists a duality between the two coverage problems, and then solve the two problems together. The presented placement algorithm is shown to deploy new nodes optimally in polynomial time.     

Augmented keyframe

In surveillance applications, keyframes are usually used to summarize important video contents. However, most traditional keyframe extraction approaches just select some video frames from the input video, while the information in these selected video frames are insufficient and cannot let the users perceive the events happened in the original video easily. In this paper, we propose a novel keyframe generating technique to condense the contents of a surveillance video clip captured by a static camera into a still picture (augmented keyframe). The augmented keyframe is a more meaningful keyframe augmented with representative objects, important contents (human faces, license plate, etc.), motion status (represented as icons) and some marks of the moving objects in a still picture. This new technique consists of two major phases: content extraction and content synthesis. Some testing results of the proposed augmented keyframe are also presented and compared with results obtained by the traditional keyframe approach.     

Fast codeword search algorithm using wavelet transform and partialdistance search techniques

A new fast codeword search algorithm for vector quantisers is presented. This algorithm performs a fast search in the wavelet domain of codewords using the partial distance search technique. Simulation results show that the algorithm has only 2% of the arithmetic complexity of the exhaustive search method     

A compact RCS formula for a dihedral corner reflector at arbitraryaspect angles

A compact closed-form formula for the RCS of a perfectly conducting right dihedral corner reflector at arbitrary aspect angles is presented. The approach is based on a combination of ray tracing, physical optics (PO), and the physical theory of diffraction (PTD). There is good agreement between the results obtained using the closed-form formula and those obtained by the shooting and bouncing rays (SBR) technique     

Reflection and transmission characteristics of lossy periodiccomposite structures

A periodic surface integral formulation is proposed to analyze the reflection and transmission properties of a lossy periodic composite structure which has circular conducting fibers embedded in a dielectric matrix. This formulation is based on the equivalence principle which represents the unknown electric and magnetic currents over the material discontinuity interfaces, and uses the structure periodicity and Poisson summation formula to reduce the problem to a periodic cell. These surface integral equations are then solved numerically, using the method of moments with pulse bases and point matching. Only the transverse magnetic (TM) case is analyzed and the numerical results such as reflected, transmitted, and dissipated powers for a single-layer fiber-reinforced composite structure are presented, in detail, to discuss the effects of frequency, incident angle, fiber radius, fiber conductivity, embedding dielectric, etc. A convergence study and a comparison with the previous published results are also included to confirm the accuracy of the new formulation     

Investigation of Thermosonic Wire Bonding Resistance of Gold Wire Onto Copper Pad

This paper discusses the electric performance for thermosonic wire bonding of gold wire onto copper pads. Various methods normally used to improve bondability were investigated including the bare copper pads with argon shielding gas and the copper pads with cupric oxide film, cuprous oxide film, and silver film. The micro-contact theory was used to determine the effective contact area. The circuit contact resistance was measured for each sample and was presented in terms of ultrasound power and effective contact area. The results show that the increase in the effective contact area leads to a lower circuit contact resistance before reaching a minimum value, and further increase in the effective contact area would not have noticeable effect on the resistance.      

Performance and reliability design issues for deep-submicrometerMOSFETs

Device design constraints, such as threshold voltage variation due to short-channel and drain-induced-barrier-lowering effects, off-state leakage current due to punchthrough and gate-induced drain leakage, hot-carrier effects such as hot-electron degradation and avalanche breakdown, and time-dependent dielectric breakdown, are examined. The current-driving capability, ring-oscillator switching speed, and small-signal voltage gain are examined. The impact that each of these factors has on the allowable choice of MOSFET channel length, oxide thickness, and power supply voltage is examined. Based on experimental results, a set of design curves, using a set of typical performance and reliability criteria, is presented for deep-submicrometer nonlightly doped drain (non-LDD) n-channel devices. From these curves, the relative importance of each particular performance/reliability mechanism for a given technology and design criteria can be determined. Because the performance and reliability issues addressed are also relevant to other MOSFET technologies, the design guidelines can also be extended to other technologies, including p-channel and LDD devices     

Scattering from a cavity-backed slit in a ground plane-TM case

Two-dimensional transverse-magnetic wave scattering from a cavity-backed slit in a ground plane is analyzed by the Harrington-Mautz generalized network formulation (1976). The admittance matrix of the cavity of arbitrary shape and medium is obtained by the finite-element method. The computed admittance matrix, added to the radiation admittance matrix of the equivalent magnetic current on a ground plane, is used to find a solution for the equivalent magnetic current on the slit. Numerical results for coated staggered cavities are included. Accurate results for the magnetic surface currents and radiation patterns have been obtained