We studied nitrogen incorporation in Al2O3 gate dielectrics by nitrogen plasma and examined the dependence of the electrical properties on the nitrogen incorporation. We found that the nitrogen concentration and profile in Al2O3 films thinner than 3 nm can be controlled by the substrate temperature and the plasma conditions. The electrical characterization showed that the plasma nitridation suppresses charges in Al2O3 films and prevents dopant penetration through the gate dielectric without increasing the leakage current or the interfacial trap density. We also demonstrated the improved performance of a metal-oxide-semiconductor field effect transistor by using a plasma nitrided Al2O3 gate dielectric. These results indicate that plasma nitridation is a promising method for improving the electrical properties of Al2O3 gate dielectrics.

Recently, Camenisch et al. and Fischlin proposed provably secure signature schemes in the standard models respectively. In this letter, we propose key substitution attacks on these two signature schemes. We show that an adversary can generate a valid public key corresponding to a legitimate signature.

It is inevitable for driver assist and warning systems to consider the drivers' state of consciousness. Drowsiness is one of the important factors in estimating the drivers' state of consciousness. A Method to extract the driver's initial stage of drowsiness was developed by means of the eyelid's opening relevant to each various characteristic of objects with motion pictures processing in the actual driving environment. The result was that an increase of the long eyelid closure time was the key factor in estimating the initial stage of drivers' drowsiness while driving. And the state of drowsiness could be presumed by checking the frequencies of long eyelid closure time per unit period.

A polarization switchable slot-coupled microstrip antenna using PIN diodes is proposed and studied. The microstrip feed line installed behind the ground plane is divided into two branches and each tip of the branches is connected to the ground plane through a PIN diode. One of the diodes is oriented from the tip to the ground plane and the other is oriented from the ground to the tip so that a slot in the ground can be selected to feed the patch by switching the dc bias between positive and negative. This selection contributes to switch the polarization between horizontal and vertical. In this paper, the authors investigate the polarization switching antenna theoretically and experimentally and confirmed sufficient differencce of antenna gain between horizontal and vertical polarization.

The authors have performed a simple computer simulation for a topography that models change in propagation characteristics due to change in traffic volume. The results of this simulation revealed that path loss for a traffic volume of about 2000 vehicles every 30 minutes in a typical urban environment exhibits a Rayleigh distribution. This result agrees well with that of actual measurements demonstrating that even a simple simulation can be a useful tool in system design.

In this paper, we propose OOK-CDMA system with optical hard-limiters (OHLs) using schemes of transmitting optical pulses with two-level intensities. The proposed system can be applied to both cases with single OHL and double OHLs. In the proposed system, a frame corresponding to a bit time is divided into two frames, where the low intensity pulses are transmitted in the weighted positions at the former frame, and the high ones are transmitted in the weighted positions at the latter frame. At the receiver side, in each weighted position of low intensity level, the ability of Multiple Access Interferences (MAIs) cancellation by OHL is equal to that of the conventional systems. However, in each weighted position of high intensity level, the OHL with the higher-level threshold value can easily eliminate MAIs with low intensity, while the MAIs are not eliminated in the conventional system. As a result, the ability of interference cancellation by OHL is significantly increased. When using single OHL in the proposed system, the optimum combinations of the values of low-level weights and low-level intensity ratio depend on the received laser power. This means that deploying dynamic control of the values of low-level weights and low-level intensity ratio is an imperative requirement in the proposed system with single OHL. On the other hand, when using double OHLs, the optimum combinations of the values of low-level weights and low-level intensity ratio are always constant. We analyze the performance of the proposed system and show its advantage in terms of bit error probability compared to the conventional system in both cases with single OHL and double OHLs. We also show that the proposed system with double OHLs is more effective and practical than the one with single OHL depending on the received laser power.

This paper describes the performance improvement of power amplifiers by defected ground structure (DGS). Due to the excellent capability of harmonic rejection and tuning, DGS plays a great role in improving the major nonlinear behaviors of power amplifier such as output power, harmonics, power added efficiency (PAE), and the ratio between the carrier and the third order intermodulation distortion (C/IMD3). In order to verify the improvement of performances by DGS, measured data for a power amplifier, which adopts a 30 Watts LDMOS device for the operation at 2.1-2.2 GHz, are illustrated under several operating bias currents for two cases, i.e., with and without DGS attached. The principle of the improvement is described by the simple Volterra nonlinear transfer functions with the consideration of different operating classes. The obtained improvement of the 30 Watts power amplifier, under 400 mA of IdsQ as an example, includes the reduction in the second and third harmonics by 17 dB and 20 dB, and the increase in output power, PAE, and C/IMD3 by 1.3 Watts, 3.4%, and 4.7 dB, respectively.

A mobile ad hoc network (MANET) is characterized by multi-hop wireless links in the absence of any cellular infrastructure as well as by frequent host mobility. This paper proposes a SMPQ: Spiral-Multi-Path QoS routing protocol in a MANET, while the MAC sub-layer adopts the CDMA-over-TDMA channel model. This work investigates the bandwidth reservation problem of on-demand QoS routing in a wireless mobile ad-hoc network. The proposed approach increases the ability of a route to identify a robust path, namely a spiral-multi-path, from source host to destination host, in a MANET to satisfy certain bandwidth requirements. Two important contributions of the proposed spiral-multi-path are: (1) the spiral-multi-path strengthens route-robustness and route-stability properties and (2) the spiral-multi-path increases the success rate of finding the QoS route. Performance analysis results demonstrate that our SMPQ protocol outperforms other protocols.

A new method to extract retinal blood vessels from a colour fundus image is described. Digital colour fundus images are contrast enhanced in order to obtain sharp edges. The green bands are selected and transformed to correlation coefficient images by using two sets of Gaussian kernel patches of distinct scales of resolution. Blood vessels are then extracted by means of a new algorithm, directional recursive region growing segmentation or D-RRGS. The segmentation results have been compared with clinically-generated ground truth and evaluated in terms of sensitivity and specificity. The results are encouraging and will be used for further application such as blood vessel diameter measurement.

A cache replacement policy which takes the transcoding time into account in making replacement decisions, for the emerging transcoding proxy servers is proposed. Simulation results show the proposed policy outperforms the conventional LRU in both the cache hit rate and the average object transcoding time.

Recently, Hwang and Li proposed a smartcard-based remote user authentication scheme. Later, Chan and Cheng showed that Hwang and Li's scheme is insecure against a kind of impersonation attack where a legitimate user can create another valid pair of user identity and password without knowing the secret key of the remote system. However, an assumption under Chan and Cheng's attack is that the attacker must be a legal user. In this paper, we further present a more fundamental and efficient impersonation attack on Hwang and Li's scheme. Using our attack, any users (including legal and illegal users) can easily get a specific legal user's password, impersonate this specific user to login to the remote system, and pass the system authentication.

This paper deals with a first evaluation of the efficiency and the robustness of the real-time "v-disparity" algorithm in stereovision for generic road obstacles detection towards various types of obstacles (vehicle, pedestrian, motorbike, cyclist, boxes) and under adverse conditions (day, night, rain, glowing effect, noise and false matches in the disparity map). The theoretical good properties of the "v-disparity" algorithm--accuracy, robustness, computational speed--are experimentally confirmed. The good results obtained allow us to use this stereo algorithm as the onboard perception process for Driving Safety Assistance: conductor warning and longitudinal control of a low speed automated vehicle (using a second order sliding mode control) in difficult and original situations, at frame rate using no special hardware. Results of experiments--Vehicle following at low speed, Stop'n'Go, Stop on Obstacle (pedestrian, fallen motorbike, load dropping obstacle)--are presented.

This paper proposes a robust method for estimating the fundamental frequency (F0) in real environments. It is assumed that the spectral structure of real environmental noise varies momentarily and its energy does not distribute evenly in the time-frequency domain. Therefore, segmenting a spectrogram of speech mixed with environmental noise into narrow time-frequency regions will produce low-noise regions in which the signal-to-noise ratio is high. The proposed method estimates F0 from the periodic and harmonic features that are clearly observed in the low-noise regions. It first uses two kinds of spectrogram, one with high frequency resolution and another with high temporal resolution, to represent the periodic and harmonic features corresponding to F0. Next, the method segments these two kinds of feature plane into narrow time-frequency regions, and calculates the probability function of F0 for each region. It then utilizes the entropy of the probability function as weight to emphasize the probability function in the low-noise region and to enhance noise robustness. Finally, the probability functions are grouped in each time, and F0 is obtained as the frequency with the highest probability of the function. The experimental results showed that, in comparison with other approaches such as the cepstrum method and the autocorrelation method, the developed method can more robustly estimate F0s from speech in the presence of band-limited noise and car noise.

This paper presents practical modeling procedure of feed patterns, bond wires, and interconnects for microwave bare-chip devices. Dedicated test structures have been designed for the process. Modeling accuracy of BJTs and diodes has been unprecedentedly improved up to 30 GHz with this procedure despite popular SPICE models were used.

Extensive studies have been made of the public key cryptosystems based on multivariate polynomials. However most of the proposed public key cryptosystems of rate 1.0 based on multivariate polynomials, are proved not secure. In this paper, we propose several types of new constructions of public key cryptosystems based on two classes of randomly generated simultaneous equations, namely, a class based on bijective transformation and another class based on random transformation. One of the features of the proposed cryptosystems is that the sets of random simultaneous equations significantly improve the utilization factor of the transformation. We show an example of the proposed cryptosystem whose size of the ciphertext is only 100 bits.

Adaptive background techniques are useful for a wide spectrum of applications, ranging from security surveillance, traffic monitoring to medical and space imaging. With a properly estimated background, moving or new objects can be easily detected and tracked. Existing techniques are not suitable for real-world implementation, either because they are slow or because they do not perform well in the presence of frequent outliers or camera motion. We address the issue by computing a learning rate for each pixel, a function of a local confidence value that estimates whether a pixel is (or not) an outlier, and a global correlation value that detects camera motion. After discussing the role of each parameter, we report experimental results, showing that our technique is fast but efficient, even in a real-world situation. Furthermore, we show that the same method applies equally well to a 3-camera stereoscopic system for depth perception.

Multiple antenna systems are promising architectures for overcoming the effects of multi-path interference and increasing the spectrum efficiency. In order to be able to investigate these systems, in this article, we derive generalized spatial correlation equations of a circular antenna array for two typical angular energy distributions: a Gaussian angle distribution and uniform angular distribution. The generalized spatial correlation equations are investigated carefully by exact and approximate analyses.

A new robust extended Kalman filter is proposed for the discrete-time nonlinear systems with norm-bounded parameter uncertainties. After linearization of the nonlinear systems, the uncertainties described by the energy bounded constraint can be converted into an indefinite quadratic cost function to be minimized. The solution to the minimization problem is given by the extended Kalman filter derived in a Krein space, which leads to a robust version of the extended Kalman filter. Since the resulting robust filter has the same structure as a standard extended Kalman filter, the proposed filter can be readily designed by simply including the uncertainty terms in its formulas. The results of simulations are presented to demonstrate that the proposed filter achieves the robustness against parameter variation and performs better than the standard extended Kalman filter.

This paper investigates the performance of an integrated voice/data wireless mobile network where a finite buffer is provided for voice calls since they can endure a tolerable time, or the reneging time, for service. Based on a given humanistic reneging time, we analyze the voice traffic blocking probability. The probability distribution of receiving service within the reneging time is obtained for each buffered voice call and based on this result, an appropriate amount of voice buffer is obtained. To alleviate the impact on data blocking probability caused by the voice buffer and to enhance the efficiency of data service, a dynamic multi-channel allocation scheme with channel de-allocation and guard channels is proposed for data traffic. Compared with the conventional method where the system adopts a single-channel allocation scheme without guard channel for data users, the proposed scheme shows significant improvement in data blocking probability, throughput and the mean service time. Furthermore, a system with an appropriate size of buffer for voice traffic can receive good improvement in voice blocking probability.

The electromagnetic scattering of a plane wave by an inhomogeneous plane whose surface impedance changes locally on the plane is treated. A boundary-value problem is formulated to describe the scattering phenomenon, in which the boundary condition depends on the surface impedance of the plane. Application of the Fourier transform derives an integral equation, which is approximately solved by the method of least-squares. From the solution of the equation, the scattered field is obtained by the inverse Fourier transform. By the use of the incomplete Lipschitz-Hankel integral for the computation of the field, numerical examples are given and the scattering phenomenon is discussed.