This paper examines polarimetric scattering characteristics caused by a dihedral corner reflector of finite size. The dihedral corner reflector is a basic model of double-bounce structure in urban area. The detailed scattering information serves the interpretation of Polarimetric Synthetic Aperture Radar (POLSAR) data analysis. The Finite-Difference Time-Domain (FDTD) method is utilized for the scattering calculation because of its simplicity and flexibility in the target shape modeling. This paper points out that there exists a stable double-bounce squint angle region both for perfect electric conductor (PEC) and dielectric corner reflectors. Beyond this stable squint angular region, the scattering characteristics become completely different from the assumed response. A criterion on the double-bounce scattering is proposed based on the physical optics (PO) approximation. The detailed analyses on the polarimetric index (co-polarization ratio) with respect to squint angle and an experimental result measured in an anechoic chamber are shown.

This letter proposes the thinnest hybrid EM wave absorber using a composite magnetic material, which can be applied to the 3 m semi anechoic chambers. We experimentally designed a new hybrid EM wave absorber of the wedge shape, which was made from the ferrite powder, the inorganic fiber and binder. As a result, the length of this absorber could be realized only 6 cm, which was ascertained having the nonflammable. The 3 m semi anechoic chamber is constructed in the size of L9 mW6 mH5.7 m using this absorber, and then the site attenuation is measured according to ANSI C63.4 in the frequency range of 30 MHz-1 GHz. As a result, the measured normalized site attenuation is obtained within 3 dB to the theoretical normalized site attenuation.

In this paper, we present a new class of public-key cryptosystem (PKC) using algebraic coding on the basis of superimposition and randomness. The proposed PKC is featured by a generator matrix, in a characteristic form, where the generator matrix of an algebraic code is repeatedly used along with the generator matrix of a random code, as sub-matrices. This generator matrix, in the characteristic form, will be referred to as K-matrix. We show that the K-matrix yields the following advantages compared with the conventional schemes: (i) It realizes an abundant supply of PKCs, yielding more secure PKCs, (ii) It realizes a short public key.

Based on the concept of Equivalent Transformation Method of Material Constant (ETMMC), a thin and light weight EM-wave absorber is newly proposed. It becomes possible to merge both the competing characteristics of changing the matching frequency toward a higher frequency region by means of punching out small holes in the magnetic absorber and of changing the matching frequency toward a lower frequency region by attaching periodical conductive patterns to the surface of it. First, the ETMMC idea is introduced in this paper. The detailed matching characteristics of the present absorber are investigated based on FDTD analysis. The matching mechanism is clarified from input admittance chart viewpoints. The matching characteristics can be changed from 2.4 GHz to above 6.0 GHz using carbonyl iron with the thickness of 2 mm and improved below -20 dB.

We propose a new security class, called plaintext simulatability, defined over the public-key encryption schemes. The notion of plaintext simulatability (denoted PS) is similar to the notion of plaintext awareness (denoted PA) defined in [3], but it is "properly" a weaker security class for public-key encryption. It is known that PA implies the class of CCA2-secure encryption (denoted IND-CCA2) but not vice versa. In most cases, PA is "unnecessarily" strong--In such cases, PA is only used to study that the public-key encryption scheme involved meets IND-CCA2, because it looks much easier to treat the membership of PA than to do "directly" the membership of IND-CCA2. We show that PS also implies IND-CCA2, while preserving such a technical advantage as well as PA. We present two novel CCA2-secure public-key encryption schemes, which should have been provided with more complicated security analyses. One is a random-oracle version of Dolev-Dwork-Naor's encryption scheme [8],[9]. Unlike the original scheme, this construction is efficient. The other is a public-key encryption scheme based on a strong pseudo-random permutation family [16] which provides the optimal ciphertext lengths for verifying the validity of ciphertexts, i.e., (ciphertext size) = (message size) + (randomness size). According to [19], such a construction remains open. Both schemes meet PS but not PA.

Digital watermarking used for fingerprinting may receive a collusion attack; two or more users collude, compare their data, find a part of embedded watermarks, and make an unauthorized copy by masking their identities. In this paper, assuming that at most c users collude, we give a characterization of the fingerprinting codes that have the best security index in a sense of "(c,p/q)-secureness" proposed by Orihara et al. The characterization is expressed in terms of intersecting families of sets. Using a block design, we also show that a distributor of data can only find asymptotically a set of c users including at least one culprit, no matter how good fingerprinting code is used.

In this paper authorization-limited transformation-free proxy cryptosystems (AL-TFP systems) are studied. It is a modification of the original proxy cryptosystem introduced by Mambo et al.[8] in which a ciphertext transformation by the original decryptor is necessary, and also a modification of the delegated decryption system proposed by Mu et al.[10]. In both systems proposed in [8] and [10], the original decryptors have to trust their proxies completely. The AL-TFP system allows the proxy decryptor to do decryption directly without any ciphertext transformation from the original decryptor, so that it can release the original decryptor more efficiently from a large amount of decrypting operations. Moreover, the original decryptor's privacy can be protected efficiently because the authority of proxy decryptor is limited to his duty and valid period. An active identity-based and a directory-based AL-TFP systems from pairings are proposed. Furthermore, an application of directory-based AL-TFP system to electronic commerce is also described. The securities of our schemes introduced are based on the BDH assumption.

XML query processing is one of the most active areas of database research. Although the main focus of past research has been the processing of structural XML queries, there are growing demands for a full-text search for XML documents. In this paper, we propose XICS (XML Indices for Content and Structural search), which aims at high-speed processing of both full-text and structural queries in XML documents. An important design principle of our indices is the use of a B+-tree. To represent the structural information of XML trees, each node in the XML tree is labeled with an identifier. The identifier contains an integer number representing the path information from the root node. XICS consist of two types of indices, the COB-tree (COntent B+-tree) and the STB-tree (STructure B+-tree). The search keys of the COB-tree are a pair of text fragments in the XML document and the identifiers of the leaf nodes that contain the text, whereas the search keys of the STB-tree are the node identifiers. By using a node identifier in the search keys, we can retrieve only the entries that match the path information in the query. The STB-tree can filter nodes using structural conditions in queries, while the COB-tree can filter nodes using text conditions. We have implemented a COB-tree and an STB-tree using GiST and examined index size and query processing time. Our experimental results show the efficiency of XICS in query processing.

In this paper, we demonstrate an immersive and interactive broadcasting production system with a new haptically enhanced multimedia broadcasting chain. The system adapts Augmented Reality (AR) techniques, which merges captured videos and virtual 3D media seamlessly through multimedia streaming technology, and haptic interaction technology in near real-time. In this system, viewers at the haptic multimedia client can interact with AR broadcasting production transmitted via communication network. We demonstrate two test applications, which show that the addition of AR- and haptic-interaction to the conventional audio-visual contents can improve immersiveness and interactivity of viewers with rich contents service.

This paper presents a new type of wearable teleoperation system that can be applied to the control of a humanoid robot. The proposed system has self-contained computing hardware with a stereo head-mounted display, a microphone, a set of headphones, and a wireless LAN. It also has a mechanism that tracks arm and head motion by using several types of sensors that detect the motion data of an operator, along with a simple force reflection mechanism that uses vibration motors at appropriate joints. For remote tasks, we use intelligent self-sensory feedback and autonomous behavior, such as automatic grasping and obstacle avoidance in a slave robot, and we feed the information back to an operator through a multimodal communication channel. Through this teleoperation system, we successfully demonstrate several teleoperative tasks, including object manipulation and mobile platform control of a humanoid robot.

Digital watermarks on pictures are more useful when they are better able to survive image processing operations and when they cause less degradation of picture quality. Random geometric distortion is one of the most difficult kinds of image processing for watermarks to survive because of the difficulty of synchronizing the expected watermark patterns to the watermarks embedded in pictures. This paper proposes three methods to improve a previous method that is not affected by this difficulty but that is insufficient in maintaining picture quality and treating other problems in surviving image processing. The first method determines the watermark strength in L*u*v* space, where human-perceived degradation of picture quality can be measured in terms of Euclidian distance, but embeds and detects watermarks in YUV space, where the detection is more reliable. The second method, based on the knowledge of image quantization, uses the messiness of color planes to hide watermarks. The third method reduces detection noises by preprocessing the watermarked image with orientation-sensitive image filtering, which is especially effective in picture portions where pixel values change drastically. Subjective evaluations have shown that these methods improved the picture quality of the previous method by 0.5 point of the mean evaluation score at the representative example case. On the other hand, the watermark strength of the previous method could be increased by 30% through 60% while keeping the same picture quality. Robustness to image processing has been evaluated for random geometric distortion, JPEG compression, Gaussian noise addition, and median filtering and it was clarified that these methods reduced the detection error ratio to 1/10 through 1/4. These methods can be applied not only to the previous method but also to other types of pixel-domain watermarking such as the Patchwork watermarking method and, with modification, to frequency-domain watermarking.

In this letter, a pilot structure and an efficient algorithm for downlink synchronization and cell searching in OFDM-based cellular systems are proposed. The pilots, randomly allocated in the frequency domain, allow us to minimize inter-cell interference (ICI) as well as to increase cell searching capability, estimation range of integer carrier frequency offset (CFO), and estimation accuracy of symbol timing offset (STO). The proposed low-complexity joint algorithm for integer CFO estimation, cell searching, and downlink detection is robust to ICI, multipath channel, STO and fine CFO.

The newest video coding standard called H.264 provides considerable performance improvement over a wide range of bit rates and video resolutions compared to previous standards. However, these features result in an extraordinary increase in encoder complexity, mainly regarding to mode decision and multiple reference frame motion estimation (ME). This letter presents two algorithms to reduce the computational complexity caused by motion estimation. The adaptive search range decision method determines the search range size according to the motion vector predictor dynamically and the early termination scheme defines a criterion to early terminate the search processing for multiple reference frames. Experimental results show that the proposed algorithms provide significant improvement of coding speed with negligible objective quality degradation compared to the fast motion estimation algorithms adopted by reference software.

Machine learning and data mining algorithms are increasingly being used in the intrusion detection systems (IDS), but their performances are laggard to some extent especially applied in network based intrusion detection: the larger load of network traffic monitoring requires more efficient algorithm in practice. In this paper, we propose and design an anomaly intrusion detection (AID) system based on the vector quantization (VQ) which is widely used for data compression and high-dimension multimedia data index. The design procedure optimizes the performance of intrusion detection by jointly accounting for accurate usage profile modeling by the VQ codebook and fast similarity measures between feature vectors to reduce the computational cost. The former is just the key of getting high detection rate and the later is the footstone of guaranteeing efficiency and real-time style of intrusion detection. Experiment comparisons to other related researches show that the performance of intrusion detection is improved greatly.

This paper presents new algorithms for the Tate pairing on a prime field. Recently, many pairing-based cryptographic schemes have been proposed. However, computing pairings incurs a high computational cost and represents the bottleneck to using pairings in actual protocols. This paper shows that the proposed algorithms reduce the cost of multiplication and inversion on an extension field, and reduce the number of calculations of the extended finite field. This paper also discusses the optimal algorithm to be used for each pairing parameter and shows that the total computational cost is reduced by 50% if k = 6 and 57% if k = 8.

To find the best transformation between a "model" point set and an "image" point set is the main purpose of point pattern matching. The similarity measure plays a pivotal role and is used to determine the degree of resemblance between two objects. Although some well-known Hausdorff distance measures work well for this task, they are very computationally expensive and suffer from the noise points. In this paper, we propose a novel similarity measure using the Hilbert curve named Hilbert scanning distance (HSD) to resolve the problems. This method computes the distance measure in the one-dimensional (1-D) sequence instead of in the two-dimensional (2-D) space, which greatly reduces the computational complexity. By applying a threshold elimination function, large distance values caused by noise and position errors (e.g. those that occur with feature or edge extraction) are removed. The proposed algorithm has been applied to the task of matching edge maps with noise. The experimental results show that HSD can provide sufficient information for image matching within low computational complexity. We believe this sets a new direction for the research of point pattern recognition.

We have proposed Rate-based Multi-path Transmission Control Protocol (R-M/TCP) for improving reliability and performance of data transfer over the Internet by using multiple paths. Congestion control in R-M/TCP is performed in a rate-based and loss-avoidance manner. It attempts to estimate the available bandwidth and the queue length of the used routes in order to fully utilize the bandwidth resources. However, it has been reported that when the used routes' characteristics, i.e. available bandwidth and delay, are much different, R-M/TCP cannot achieve the desired throughput from the routes. This is because R-M/TCP originally transmits data packets in a round-robin manner through the routes. In this paper, therefore, we propose R-M/TCP using Packet Scheduling Algorithm (PSA). Instead of using the round-robin manner, R-M/TCP utilizes PSA that accounts for time-varying bandwidth and delay of each path so that number of data packets arriving in out-of-order at the receiver can be minimized and the desired throughput can be achieved. Quantitative simulations are conducted to show effectiveness of R-M/TCP using PSA.

Finding intracranial aneurysms plays a key role in preventing serious cerebral diseases such as subarachnoid hemorrhage. For detection of aneurysms, magnetic resonance angiography (MRA) can provide detailed images of arteries non-invasively. However, because over 100 MRA images per subject are required to cover the entire cerebrum, image diagnosis using MRA is very time-consuming and labor-intensive. This article presents a computer-aided diagnosis (CAD) system for finding aneurysms with MRA images. The principal components are identification of aneurysm candidates (= ROIs; regions of interest) from MRA images and estimation of a fuzzy degree for each aneurysm candidate based on a case-based reasoning (CBR). The fuzzy degree indicates whether a candidate is true aneurysm. Our system presents users with a limited number of ROIs that have been sorted in order of fuzzy degree. Thus, this system can decrease the time and the labor required for detecting aneurysms. Experimental results using phantoms indicate that the system can detect all aneurysms at branches of arteries and all saccular aneurysms produced by dilation of a straight artery in 1 direction perpendicular to the principal axis. In a clinical evaluation, performance in finding aneurysms and estimating the fuzzy degree was examined by applying the system to 16 subjects with a total of 19 aneurysms. The experimental results indicate that this CAD system detected all aneurysms except a fusiform aneurysm, and gave high fuzzy degrees and high priorities for the detected aneurysms.

Security protocols flaws represent a substantial portion of security exposures of data networks. In order to evaluate security protocols against any attack, formal methods are equipped with a number of techniques. Unfortunately, formal methods are applicable for static state only, and don't guarantee detecting all possible flaws. Therefore, formal methods should be complemented with dynamic protection. Anomaly detection systems are very suitable for security protocols environments as dynamic activities protectors. This paper presents an intrusion detection system that uses a number of different anomaly detection techniques to detect attacks against security protocols.

Since sentences are the basic propositional units of text, knowing their themes should help in completing various tasks such as automatic summarization requiring the knowledge about the semantic content of text. Despite the importance of determining the theme of a sentence, however, few studies have investigated the problem of automatically assigning a theme to a sentence. In this paper, we examine the notion of sentence theme and propose an automatic scheme where head-driven patterns are used for theme assignment. We tested our scheme with sentences in encyclopedia articles and obtained a promising result of 98.96% in F-score for training data and 88.57% for testing data, which outperform the baseline using all but the head-driven patterns.