A low-power Ku-band downconverter in InGaP-GaAs HBT technology

We have developed a low-voltage, low-power Ku-band microwave monolithic integrated circuit (MMIC) downconverter using InGaP-GaAs heterojunction bipolar transistor technology. It consists of a preamplifier, a double-balanced mixer, and an L-band wideband intermediate-frequency (IF) amplifier. The downconverter achieves a conversion gain of 31 dB, with a gain flatness within /spl plusmn/ 1 dB, and an output-referred 1-dB compression power (P/sub 1dB,OUT/) of +2.5dBm. This downconverter dissipates 33mA from a 3-V supply. We believe that the operating voltage and power consumption are lower than those of previously published Ku-band MMIC downconverters.     

Waveband-switchable SOA ring laser constructed with a phase modulator loop mirror filter

An electrically tunable multiwavelength source has been developed using a birefringence-based optical comb filter in a semiconductor optical amplifier ring laser. The filter is constructed with an electrooptic phase modulator placed inside a fiber loop mirror. By controlling the birefringence of the modulator through the applied bias, the radio-frequency power, or the modulation frequency, we achieve a continuous shift of the spectral comb to access different interleaved wavebands. Electrical waveband switching has been successfully demonstrated for 21 wavelengths at 100-GHz grid spacing with an optical signal-to-noise ratio over 40 dB.     

An Intelligent Product Recommendation Model to Reflect the Recent Purchasing Patterns of Customers

Mobile Networks and Applications - This study suggests a new product recommendation model to reflect the recent purchasing patterns of customers. There are many methods to measure the similarity...     

Estimation of lung's air volume and its variations throughout respiratory CT image sequences

A respiratory image-sequence-segmentation technique is introduced based on a novel image-sequence analysis. The proposed technique is capable of segmenting the lung's air and its soft tissues followed by estimating the lung's air volume and its variations throughout the image sequence. Accurate estimation of these two parameters is very important in many applications related to lung disease diagnosis and treatment systems (e.g., brachytherapy), where the parameters are either the variables of interest themselves or are dependent/independent variables. The concept of the proposed technique involves using the image sequence's combined histogram to obtain a reasonable initial guess for the lung's air segmentation thresholds. This is followed by an optimization process to find the optimum threshold values that best satisfy the lung's air mass conservation and tissue incompressibility principles. These threshold values are consequently applied to estimate the lung's air volume and its variations throughout respiratory Computed Tomography (CT) image sequences. Ex vivo experiments were conducted on porcine left lungs in order to demonstrate the performance of the proposed technique. The proposed method was initially validated using a breath-hold CT image sequence with known air volumes inside the lung, where results show that the proposed technique outperforms single-histogram-based methods. This was followed by demonstrating the proposed technique's application in a 4-D-CT respiratory sequence, where the air volume inside the lung was unknown. Consistency of the obtained results in the latter experiment with tissue near incompressibility principle was validated. The results indicate a very good ability of the proposed method for estimating the lung's air volume and its variations in a respiratory image sequence.     

Improved Shamir's CRT‐RSA Algorithm: Revisit with the Modulus Chaining Method

RSA signature algorithms using the Chinese remainder theorem (CRT‐RSA) are approximately four‐times faster than straightforward implementations of an RSA cryptosystem. However, the CRT‐RSA is known to be vulnerable to fault attacks; even one execution of the algorithm is sufficient to reveal the secret keys. Over the past few years, several countermeasures against CRT‐RSA fault attacks have tended to involve additional exponentiations or inversions, and in most cases, they are also vulnerable to new variants of fault attacks. In this paper, we review how Shamir's countermeasure can be broken by fault attacks and improve the countermeasure to prevent future fault attacks, with the added benefit of low additional costs. In our experiment, we use the side‐channel analysis resistance framework system, a fault injection testing and verification system, which enables us to inject a fault into the right position, even to within 1 μs. We also explain how to find the exact timing of the target operation using an Atmega128 software board.     

Information loss recovery for block-based image coding techniques-afuzzy logic approach

A new technique to recover the information loss in a block-based image coding system is developed in this paper. The proposed scheme is based on fuzzy logic reasoning and can be divided into three main steps: (1) hierarchical compass interpolation/extrapolation (HCIE) in the spatial domain for initial recovery of lost blocks that mainly contain low-frequency information such as smooth background (2) coarse spectra interpretation by fuzzy logic reasoning for recovery of lost blocks that contain high-frequency information such as complex textures and fine features (3) sliding window iteration (SWI), which is performed in both spatial and spectral domains to efficiently integrate the results obtained in steps (1) and (2) such that the optimal result can be achieved in terms of surface continuity on block boundaries and a set of fuzzy inference rules. The proposed method, which is suitable for recovering both isolated and contiguous block losses, provides a new approach for error concealment of block-based image coding systems such as the JPEG coding standard and vector quantization-based coding algorithms. The principle of the proposed scheme can also be applied to block-based video compression schemes such as the H.261, MPEG, and HDTV standards. Simulation results are presented to illustrate the effectiveness of the proposed method.     

Scanning tomographic acoustic microscopy

The scanning tomographic acoustic microscope (STAM) was proposed in 1982 as a method of improving the resolution capability of the scanning laser acoustic microscope (SLAM) based on the principles of tomography. By modifying the SLAM with a quadrature detector, tomographic projections that contain both the amplitude and phase information of the scattered wavefield can be acquired. Subsequently, multiple projections acquired with different incident waves are combined using the "back-and-forth" propagation algorithm to form the tomographic reconstruction. The first STAM reconstructions have been obtained to experimentally demonstrate the superior resolution capability of the STAM over the SLAM. In this paper, the implementation of the STAM is described, and experimental reconstructions of multiple-layer specimens are demonstrated.