0.8 V CMOS adiabatic differential switch logic circuit using bootstrap technique for low-voltage low-power VLSI

A novel 0.8 V CMOS adiabatic differential switch logic (ADSL) circuit using the bootstrap technique for low-voltage low-power VLSI is reported. Using capacitance coupling effects from the bootstrap transistors with the related isolating transistors, this 0.8 VADSL circuit has a 52% smaller propagation delay time, consuming 26% less power as compared to the energy efficient logic circuit.     

Cryptanalysis of Hsiang‐Shih's authentication scheme for multi‐server architecture

From user point of view, password‐based remote user authentication technique is one of the most convenient and easy‐to‐use mechanisms to provide necessary security on system access. As the number of computer crimes in modern cyberspace has increased dramatically, the robustness of password‐based authentication schemes has been investigated by industries and organizations in recent years. In this paper, a well‐designed password‐based authentication protocol for multi‐server communication environment, introduced by Hsiang and Shih, is evaluated. Our security analysis indicates that their scheme is insecure against session key disclosure, server spoofing attack, and replay attack and behavior denial. Copyright © 2010 John Wiley & Sons, Ltd.     

Hierarchical B-picture mode decision in H.264/SVC

To enable robust video transmission over heterogeneous networks, the hierarchical B-picture prediction structure is employed in the state-of-the-art video coding standard H.264/SVC, aiming to produce scalable bitstreams with various frame rates. However, the exhaustive mode decision process with the hierarchical B-picture structure increases the computational complexity of H.264/SVC encoding dramatically. In this paper, a fast mode decision algorithm is proposed to speed up H.264/SVC encoding with the hierarchical B-picture structure, which is achieved by utilizing macroblock (MB) features, correlation of temporal–spatial neighboring MBs, and the discrepant characteristics of hierarchical layers. Extensive experimental results demonstrate that the proposed algorithm is able to reduce the encoding time of H.264/SVC significantly for video sequences with a wide range of resolutions, and meanwhile the video quality and compression ratio are well preserved.     

Time and temperature-dependent mechanical behavior of underfill materials in electronic packaging application

The thermo-mechanical testing of HYSOL FP4549 polymer-filled underfill materials was conducted under different strain rate and temperature environment. A new specimen preparation procedure and further test methodology are developed to characterize the time–temperature mechanical behaviors of underfill materials. The stress–strain behavior of materials is simulated with constitutive framework, and the dependence of Young’s modulus on temperature and strain rate was evaluated. In addition, the specimens were tested with microforce testing system to evaluate the creep curve of underfill materials as a function of temperature and stress level. In view of the uncertainty of the Young’s modulus determination, the specimens were tested with unloading–reloading technique to verify the test results and investigate its cyclic mechanical behaviors. On the other hand, the adhesion strength of underfill materials are tested between different adhesion surface by different deformation rate after some isothermal and hygro-thermal environments attack, which is to simulate the environment that the electronic components may be encountered. The results reveal that the rise of the temperature and moisture cause the apparent reduction of the surface adhesion strength, due to the microstructure transition of materials and the diffusion and concentration of moisture. For all conditions of the experiment after environmental preconditioning, the specimen fracture surfaces occur between solder mask and FR4 substrates, which means the measured strength is the adhesion strength between solder mask and FR4. Comparing different adhesion surface, the adhesion strength of underfill/FR4 is higher than solder mask/FR4. The interface of solder mask/FR4 is more sensitive to the temperature and moisture. In all of the cases, increasing the moisture level has a varying but significant effect on both fracture strength and absorption energy Ψ. The failure mode transfer and the strength degradation are attributed to the moisture uptake between the FR4/solder mask and solder mask/underfill interface.     

Confined Ferroelectric Properties in Poly(Vinylidene Fluoride‐co‐Chlorotrifluoroethylene)‐graft‐Polystyrene Graft Copolymers for Electric Energy Storage Applications

Dielectric polymer film capacitors having high energy density, low loss and fast discharge speed are highly desirable for compact and reliable electrical power systems. In this work, we study the confined ferroelectric properties in a series of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene)‐graft‐polystyrene [P(VDF‐CTFE)‐g‐PS] graft copolymers, and their potential application as high energy density and low loss capacitor films. Thin films (ca. 20 μm) are prepared by different processing methods, namely, hot‐pressing or solution‐casting followed by mechanical stretching at elevated temperatures. After crystallization‐induced microphase separation, PS side chains are segregated to the periphery of PVDF crystals, forming a confining interfacial layer. Due to the low polarizability of this confining PS‐rich layer at the amorphous–crystalline interface, the compensation polarization is substantially decreased resulting in a novel confined ferroelectric behavior in these graft copolymers. Both dielectric and ferroelectric losses are significantly reduced at the expense of a moderate decrease in discharged energy density. Our study indicates that the best performance is achieved for a P(VDF‐CTFE)‐g‐PS graft copolymer with 34 wt‐% PS; a relatively high discharged energy density of approximately 10 J cm^?3 at 600 MV m^?1, a low dielectric loss (tanδ = 0.006 at 1 kHz), and a low hysteresis loop loss (17.6%) at 550 MV m^?1.     

Nearly dispersion-penalty-free transmission using blue-shifted1.55-μm distributed feedback lasers

Nearly dispersion-penalty-free transmission over 40 km of nondispersion-shifted single-mode fiber was demonstrated using blue-shifted 1.55-μm distributed feedback lasers. This good system performance is attributed to the narrow and blue-shifted modulated optical spectrum which is in turn associated with the soft turn-on light-current characteristics. Transmission experiments using lasers with hard turn-on light-current characteristics give rise to broad modulated spectra and higher dispersion penalties     

Steering control of automated vehicles using absolute positioning GPS and magnetic markers

Steering control for passenger cars on automated highways is analyzed. The feasibility of an automatic steering system based on absolute positioning global positioning system (GPS) and a magnetic marker guidance system has been evaluated using computer simulations. State estimation and control algorithm issues are examined for such a control system. By use of GPS and a magnetic marker sensor, an accurate and real-time estimation of the vehicle's lateral displacements with respect to the road can be accomplished. A steering control algorithm based on road curvature preview for achieving good road tracking and providing ride comfort is also presented. The proposed estimation and control system are validated by simulation results.     

Microstrip stepped impedance resonator bandpass filter with an extended optimal rejection bandwidth

Bandpass filters with an optimal rejection bandwidth are designed using parallel-coupled stepped impedance resonators (SIRs). The fundamental (f/sub o/) and higher order resonant harmonics of an SIR are analyzed against the length ratio of the high-Z and low-Z segments. It is found that an optimal length ratio can be obtained for each high-Z to low-Z impedance ratio to maximize the upper rejection bandwidth. A tapped-line input/output structure is exploited to create two extra transmission zeros in the stopband. The singly loaded Q(Q/sub si/) of a tapped SIR is derived. With the aid of Q/sub si/, the two zeros can be independently tuned over a wide frequency range. When the positions of the two zeros are purposely located at the two leading higher order harmonics, the upper rejection band can be greatly extended. Chebyshev bandpass filters with spurious resonances up to 4.4f/sub o/, 6.5f/sub o/, and 8.2f/sub o/ are fabricated and measured to demonstrate the idea.     

Triple-frequency planar monopole antenna for side-feed communication device on GSM/DCS/PCS operation

A novel side-feed planar monopole antenna capable of triple-frequency operation at about 900, 1800 and 1900 MHz is presented. The planar monopole antenna occupies a small area of 6/spl times/31 mm, and is easily made using thin copper. The planar monopole antenna can be side-fed and mounted perpendicularly to the main circuit board of a communication device so that it offers a novel design with a free degree of feed point so as to save device space, resulting in a low profile to the system ground plane. In addition, the obtained impedance bandwidths of the proposed antenna at about 900, 1800 and 1900 MHz can cover the GSM (890-960 MHz), DCS (1710-1880 MHz) and PCS (1850-1990 MHz) bands.     

Characterization and Properties of Nickel Aluminide Nanocrystals in an Alumina Layer for Nonvolatile Memory Applications

Intermetallic nanocrystal memory devices with nickel aluminide nanocrystals in the electron-trapping layer and an alumina layer as the blocking layer were prepared on the surface of oxidized silicon substrates by sputter-coating of Ni and Al₂O₃ in sequence, followed by an annealing procedure. Several aluminide nanocrystal memory devices are reported. The effect of annealing at 900°C on the memory properties was investigated. Intermetallic nanocrystals were identified by high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy as Ni₂Al₃ with sizes of 15–20 nm. The results showed that a sixfold increase (0.37 V to 2.34 V) in the memory window could be achieved after annealing for the optimal time of 3 min.