A mode-matching technique in conjunction with the Floquet theorem is proposed to analyze the propagation characteristics of periodic circular surface waveguides. The circular waveguides are coated outside with a multilayered dielectric and have a ground plane with periodic corrugation of arbitrary profile. Three different ground corrugation profiles are examined to demonstrate the influences of the corrugation shape, depth, and width, dielectric thickness, and relative permittivity on bandstop characteristics.

The electrical parameters (88 LRGC matrices) of 8-coupled uniform lossy transmission lines were extracted from 40 S-parameter values measured by using 2-port VNA measurements, where all the ports other than 2 VNA ports were terminated by 50 ohm chip resistors. It was assumed in the extraction step that the transmission lines are weakly-coupled, and that the resistance values of all the termination chip resistors are exactly 50 ohms with the second reflections neglected. Comparison of the extracted LRGC matrix components with those from a commercial 3D field solver revealed on average and a maximum relative difference of 2.45% and 7.66%, respectively. In addition, the time-domain crosstalk voltage waveforms in the measured data and those in the SPICE simulation results using the extracted LRGC parameters agreed very well with the average difference and the maximum relative difference in peak crosstalk voltages of 4.15% and 9.68%, respectively.

Shadow detection and removal is important to deal with traffic image sequences. Cast shadow of vehicle may lead to an inaccurate object feature extraction and erroneous scene analysis. Furthermore, separate vehicles can be connected through shadow. Both can confuse object recognition systems. In this paper, a robust method is proposed for detecting and removing active cast shadow in monocular color image sequences. Background subtraction method is used to extract moving blobs in color and gradient dimensions, and the YCrCb color space is adopted for detecting and removing the cast shadow. Even when shadows link different vehicles, it can detect the each vehicle figure using modified mask by shadow bar. Experimental results from town scenes show that proposed method is effective and the classification accuracy is sufficient for general vehicle type classification.

In this letter, a new formula is proposed for calculating the polarization entropy, based on the least square method. There is no need to calculate the eigenvalues of a covariance matrix as well as to use logarithms of values. So the time for computing the polarization entropy is reduced. Using polarimetric SAR data, the authors validate the effectiveness of the new formula.

This paper presents a high-accuracy 3D (three-dimen-sional) measurement system using multi-camera passive stereo vision to reconstruct 3D surfaces of free form objects. The proposed system is based on an efficient stereo correspondence technique, which consists of (i) coarse-to-fine correspondence search, and (ii) outlier detection and correction, both employing phase-based image matching. The proposed sub-pixel correspondence search technique contributes to dense reconstruction of arbitrary-shaped 3D surfaces with high accuracy. The outlier detection and correction technique contributes to high reliability of reconstructed 3D points. Through a set of experiments, we show that the proposed system measures 3D surfaces of objects with sub-mm accuracy. Also, we demonstrate high-quality dense 3D reconstruction of a human face as a typical example of free form objects. The result suggests a potential possibility of our approach to be used in many computer vision applications.

The Navigational Programming (NavP) methodology is based on the principle of self-migrating computations. It is a truly incremental methodology for developing parallel programs: each step represents a functioning program, and each intermediate program is an improvement over its predecessor. The transformations are mechanical and straightforward to apply. We illustrate our methodology in the context of matrix multiplication, showing how the transformations lead from a sequential program to a fully parallel program. The NavP methodology is conducive to new ways of thinking that lead to ease of programming and high performance. Even though our parallel algorithm was derived using a sequence of mechanical transformations, it displays certain performance advantages over the classical handcrafted Gentleman's Algorithm.

In this paper, we examine the efficiency of tunneling techniques since they will accelerate multicast deployment. Our motivation is that, despite the many proposals focused on tunneling techniques, their impact on multicast efficiency has yet to be assessed sufficiently. First, the structure of multicast delivery trees is examined based on the seminal work of Phillips et al. [26]. We then quantitatively assess the impact of tunneling, such as loads imposed on the tunnel endpoints and redundant traffic. We also formulate a critical size of multicast island, above which the loads are suddenly diminished. Finally, a unique delivery tree model is introduced, which is so simple yet practical, to better understand the performance of the multicast-related protocols. This paper is the first to formulate the impact of tunneling.

We propose a real-time measurement method, DPDC (Detection of Packet-Delay Correlation), which models both available bandwidth and the averaging time scale. In this method, measurement periods are short and constant, while the theoretical measurement error is reduced. DPDC is established based on the discussion of the systematic error of the packet pair/train measurement. We evaluate through simulations its accuracy and robustness against the multihop effect. We also verify the feasibility of real-time measurements through testbed experiments using a tool called Linear that implements DPDC. Efficiency is demonstrated through simulations and testbed experiments by analyzing accidental and systematic errors. Finally, we discuss the available bandwidth variation in an Internet path using real-time data produced by Linear measurements and passive monitoring.

This study presents a fast adaptive algorithm for noise estimation in non-stationary environments. To make noise estimation adapt quickly to non-stationary noise environments, a robust entropy-based voice activity detection (VAD) is thus required. It is well-known that the entropy-based measure defined in spectral domain is very insensitive to the changing level of nose. To exploit the specific nature of straight lines existing on speech-only spectrogram, the proposed spectrum entropy measurement improved from spectrum entropy proposed by Shen et al. is further presented and is named band-splitting spectrum entropy (BSE). Consequently, the proposed recursive noise estimator including BSE-based VAD can update noise power spectrum accurately even if the noise-level quickly changes.

Let G = (V,E) be an edge weighted graph with n vertices and m edges. For a given integer p with 1 < p < n, we call a set X V of p vertices a p-maximizer if X has a property that the edge-connectivity of the graph obtained by contracting X into a single vertex is no less than that of the graph obtained by contracting any other subset of p vertices. In this paper, we first show that there always exists an ordering v1,v2,...,vn of vertices in V such that, for each i = 2,3,...,n - 1, set {v1,v2,...,vi} is an i-maximizer. We give an O(mn + n2log n) time algorithm for finding such an ordering and then show an application to the source location problem.

In RSA public-key cryptosystem, a small private key is often preferred for efficiency but such a small key could degrade security. Thus the Chinese Remainder Theorem (CRT) is tactically used, especially in time-critical applications like smart cards. As for using the CRT in RSA, care must be taken to resist partial key exposure attacks. While it is common to choose two distinct primes with similar size in RSA, May has shown that a composite modulus N can be factored in the balanced RSA with the CRT of half of the least (or most) significant bits of a private key is revealed with a small public key. However, in the case that efficiency is more critical than security, such as smart cards, unbalanced primes might be chosen. Thus, we are interested in partial key exposure attacks to the unbalanced RSA with the CRT. In this paper, we obtain the similar results as the balanced RSA. We show that in the unbalanced RSA if the N1/4 least (or most) significant bits are revealed, a private key can be recovered in polynomial time under a small public key.

In everyday life, a situation often occurs wherein two or more persons with different personal schedules must determine a single job schedule. The authors focus on the practical concept of rent and loan and propose a scheduling system. This system generates a schedule that automatically coordinates with a state involving minimum rent and loan. They also propose a method that employs the analytic network process (ANP) for setting individual priorities based on the rent and loan information. Furthermore, the authors implement the proposed system as a simulation system and verify whether it generates a fair schedule by computing the sum of the rent and loan of different individuals. The result shows that in comparison with human scheduling, the proposed method generates a fairer schedule by computing the rent and loan of each individual.

This paper proposes ABdis, a new active measurement method for estimating the available bandwidth on a communication network path. Due to the recent explosion in multimedia applications, it is becoming increasingly important to manage network QoS, and tools that can measure network quality precisely are necessary to do this. Many conventional active measurement methods/tools, however, can measure/estimate only the average of the available bandwidth in a given period but cannot measure its distribution. If the distribution of the bandwidth over short intervals can be measured, the information would be useful for network management, proxy selection, and end-to-end admission control. We propose an end-to-end active measurement method called ABdis, which can estimate the distribution of the available bandwidth in a network path. ABdis employs multiple probes having different rates and a parameter-matching technique for estimating distribution. Furthermore, we present the results of simulations and verify ABdis's performance under various conditions by changing probe parameters, amount of cross traffic, and network models.

The queue size at a bottleneck would impact the performance of TCP protocols, especially when running a single TCP flow in networks with a large bandwidth-delay product. However, queue size has been not well considered in experiments. This paper shows how bottleneck queue size influences TCP protocols performance. Bursityness of advanced TCPs is examined. Ways of estimating queue size are introduced. Sending a UDP packet train until a loss is detected is a method to measure queuing delay to estimate queue size. Watching a loss in a TCP session to measure round trip time and calculate the queue size is also discussed. Results from experiments with a network emulator and a real network are reported. The results indicated that a layer-2 switch at a congestion point would be a major factor of decreasing TCP performance in a fast long distant path.

Recently, Chien et al. proposed an efficient timestamp-based remote user authentication scheme using smart cards. The main merits include: (1) user-independent server, i.e., there is no password or verification table kept in the server; (2) users can freely choose their passwords; (3) mutual authentication is provided between the user and the server; and (4) lower communication and computation cost. In this paper, we show that Chien et al.'s scheme is insecure against forgery attack because one adversary can easily pretend to be a legal user, pass the server's verification and login to the remote system successfully. An improved scheme is proposed that can overcome the security risk while still preserving all the above advantages.

Power Spectral Density (PSD) computed by taking the Fourier transform of auto-correlation functions (Wiener-Khintchine Theorem) gives better result, in case of noisy data, as compared to the Periodogram approach in case the signal is Gaussian. However, the computational complexity of Wiener-Khintchine approach is more than that of the Periodogram approach. For the computation of short time Fourier transform (STFT), this problem becomes even more prominent where computation of PSD is required after every shift in the window under analysis. This paper presents a recursive form of PSD to reduce the complexity. If the signal is not Gaussian, the PSD approach is insufficient and we estimate the higher order spectra of the signal. Estimation of higher order spectra is even more time consuming. In this paper, recursive versions for computation of bispectrum has been presented as well. The computational complexity of PSD and bispectrum for a window size of N, are O(N) and O(N2) respectively.

In this paper, we propose a method of detecting TCP performance degradation using only bottleneck-link utilization statistics: mean and variance. The variance of link utilization normally increases as the mean link-utilization increases. However, because link-utilization has a maximum of 100%, as the mean approaches 100%, the possible range of fluctuation becomes narrow and the variance decreases to zero. In this paper, using the M/G/R processor sharing model, we relate this phenomenon to the behavior of flows. We also show that by using this relationship, we can detect TCP performance degradation using the mean and variance of link utilization. In particular, this method enables a network operator to determine whether or not the degradation originates from the congestion of his/her own network. Because our method requires us to measure only link utilization, the cost of performance management can be greatly decreased compared with the conventional method, which requires dedicated functions for directly measuring the TCP performance.

To clarify the correspondence between Shielding Effectiveness (SE) of shielding materials and their physical property, we propose an equivalent circuit for a shielding effectiveness test apparatus using a dual TEM cell, and show its validity. By considering the structure of dual TEM cell that consists of a pair of cells coupled via an aperture in their common wall, we defined the capacitance C and mutual inductance M, that respectively express the electric coupling and magnetic coupling between two center conductors. By the measurement of unloaded S-parameter, we determined the values of C and M for a dual TEM cell in hand. Next, the shielding material was approximated by the apparent sheet resistivity Rs, and was used in the equivalent circuit of loaded aperture. As a result, the coupling level calculated from the equivalent circuit agreed well with the measured data in frequencies below 300 MHz.

Traceability codes are used in schemes that prevent illegal redistribution of digital content. In this Letter, we use Chinese Reminder Theorem codes to construct traceability codes. Both the code parameters and the traitor identification process take into account the non-uniformity of the alphabet of Chinese Reminder Theorem codes. Moreover it is shown that the identification process can be done in polynomial time using list decoding techniques.

In this paper, we discuss the efficiency of tunneling techniques which are expected to accelerate multicast deployment. Our motivation is that, despite the proposal of many tunneling techniques, no paper has studied their impact on multicast efficiency. Through detailed computer experiments, we find that there is a critical size of multicast island, above which the loads imposed on tunneling endpoints are suddenly diminished. In addition, multicast islands equaling or exceeding the critical size reduce the overhead of forwarding states on routers. We also find a scaling law between the critical size and group size. Based on these findings, we present simple guidelines on using tunneling when deploying multicast systems. A possible explanation for our findings is uncovered by a simple analysis. Our work is the first to evaluate the impact of tunneling and clarify conditions in which multicast deployment is well supported by tunneling.