Observing the security of existing identity-based proxy signature schemes was proven in the random oracle model, Cao et al. proposed the first direct construction of identity-based proxy signature secure in the standard model by making use of the identity-based signature due to Paterson and Schuldt. They also provided a security proof to show their construction is secure against forgery attacks without resorting to the random oracles. Unfortunately, in this letter, we demonstrate that their scheme is vulnerable to insider attacks. Specifically, after a private-key extraction query, an adversary, behaving as a malicious original signer or a malicious proxy signer, is able to violate the unforgeability of the scheme.

This study investigated the relationship between social skills and facial asymmetry in facial expressions. Three-dimensional facial landmark data of facial expressions (neutral, happy, and angry) were obtained from Japanese participants (n = 62). Following a facial expression task, each participant completed KiSS-18 (Kikuchi's Scale of Social Skills; Kikuchi, 2007). Using a generalized Procrustes analysis, faces and their mirror-reversed versions were represented as points on a hyperplane. The asymmetry of each individual face was defined as Euclidian distance between the face and its mirror reversed face on this plane. Subtraction of the asymmetry level of a neutral face of each individual from the asymmetry level of a target emotion face was defined as the index of “expression asymmetry” given by a particular emotion. Correlation coefficients of KiSS-18 scores and expression asymmetry scores were computed for both happy and angry expressions. Significant negative correlations between KiSS-18 scores and expression asymmetries were found for both expressions. Results indicate that the symmetry in facial expressions increases with higher level of social skills.

In order to improve user's privacy in multi-authority Attribute-Based Encryption (ABE), we propose a solution which hides user's attributes by privacy homomorphism, such that not only the “external” adversary fails to access the private attribute of one user by eavesdropping on communications, but also the “internal” Attribute Authorities (AA), who are responsible for issuing attribute keys, are unable to build a full profile with all of the user's attributes by pooling their information on the user's ID. Meanwhile, the use of ID is essential to defend against collusion attack on ABE. Benefiting from privacy homomorphism, by which we distribute the part of the interpolation for the shares abstracted by the hidden attributes into each AA, the performance of the proposed scheme is higher than those of existing ABE schemes.

In this study, 2-location distance-based registration (2DBR) is proposed to improve the performance of traditional distance-based registration. In distance-based registration, when a mobile station (MS) enters a new cell, the MS calculates the distance from the last registered cell and registers its location if the calculated distance reaches a prescribed distance threshold D. In 2DBR, an MS stores not only the last registered location area (LA) but also the second-to-last LA, and then no registration is performed when the MS crosses the two stored LAs. The 2DBR may increase paging cost but it may decrease registration cost. Simulation results show that our proposed 2DBR outperforms current distance-based registration in most cases.

Subgraph matching is a fundamental operation for querying graph-structured data. Due to potential errors and noises in real-world graph data, exact subgraph matching is sometimes inappropriate in practice. In this paper we consider an approximate subgraph matching model that allows missing edges. Based on this model, approximate subgraph matching finds all occurrences of a given query graph in a database graph, allowing missing edges. A straightforward approach is to first generate query subgraphs of a given query graph by deleting edges and then perform exact subgraph matching for each query subgraph. In this paper we propose a sharing-based approach to approximate subgraph matching, called SASUM. Our method is based on the fact that query subgraphs are highly overlapped. Due to this overlapping nature of query subgraphs, the matches of a query subgraph can be computed from the matches of a smaller query subgraph, which results in reducing the number of query subgraphs that require expensive exact subgraph matching. Our method uses a lattice framework to identify sharing opportunities between query subgraphs. To further reduce the number of graphs that need exact subgraph matching, SASUM generates small base graphs that are shared by query subgraphs and chooses the minimum number of base graphs whose matches are used to derive the matching results of all query subgraphs. A comprehensive set of experiments shows that our approach outperforms the state-of-the-art approach by orders of magnitude in terms of query execution time.

Estimating a proper location of vanishing point from a single road image without any prior known camera parameters is a challenging problem due to limited information from the input image. Most edge-based methods for vanishing point detection only work well for structured roads with clear painted lines or distinct boundaries, while they usually fail in unstructured roads lacking sharply defined, smoothly curving edges. In order to overcome this limitation, texture-based methods for vanishing point detection have been widely published. Authors of these methods often calculate the texture orientation at every pixel of the road image by using directional filter banks such as Gabor wavelet filter, and seek the vanishing point by a voting scheme. A local adaptive soft voting method for obtaining the vanishing point was proposed in a previous study. Although this method is more effective and faster than prior texture-based methods, the associated computational cost is still high due to a large number of scanning pixels. On the other hand, this method leads to an estimation error in some images, in which the radius of the proposed half-disk voting region is not large enough. The goal of this paper is to reduce the computational cost and improve the performance of the algorithm. Therefore, we propose a novel local soft voting method, in which the number of scanning pixels is much reduced, and a new vanishing point candidate region is introduced to improve the estimation accuracy. The proposed method has been implemented and tested on 1000 road images which contain large variations in color, texture, lighting condition and surrounding environment. The experimental results demonstrate that this new voting method is both efficient and effective in detecting the vanishing point from a single road image and requires much less computational cost when compared to the previous voting method.

Many broadcast encryption schemes have been proposed for conventional networks. However, those schemes are not suitable for wireless sensor networks, which have very limited resources such as communication, computation, and storage. In this paper, we propose an efficient and practical identity-based broadcast encryption scheme for sensor networks by exploiting the characteristics of sensor networks: in the deployment stage, the set of neighboring sensor nodes are determined and most communications are conducted among the neighbors due to radio power limitations of the nodes. The proposed scheme features the following achievements: (1) all of the public keys and private keys are of constant size; (2) it satisfies all the security requirements for sensor networks. The proposed scheme is optimal in the sense that it requires no pairing operation when adopting pre-computation.

PCA-L1 (principal component analysis based on L1-norm maximization) is an approximate solution of L1-PCA (PCA based on the L1-norm), and has robustness against outliers compared with traditional PCA. However, the more dimensions the feature space has, the more calculation time PCA-L1 consumes. This paper focuses on an initialization procedure of PCA-L1 algorithm, and proposes a fast method of PCA-L1 using Gram-Schmidt orthogonalization. Experimental results on face recognition show that the proposed method works faster than conventional PCA-L1 without decrease of recognition accuracy.

The quantum dot optical frequency comb laser (QD-CML) is an attractive photonic device for generating a stable emission of fine multiple-wavelength peaks. In the present paper, 1.0-GHz and 10-ps-order short optical pulsation is successfully demonstrated from a hybrid mode-locked QD-CML with an ultrabroadband wavelength tuning range in the T+O band. In addition, 10-GHz high-repetition intensity-stable short optical pulse generation with a high S/N ratio is successfully demonstrated using an external-cavity QD-CML with a 10th-harmonic mode-locking technique.

This paper presents an efficient approach for logarithmic and anti-logarithmic converters which can be used in the arithmetic unit of hybrid number system processors and logarithm/exponent function generators in DSP applications. By employing the novel quasi-symmetrical difference method with only the simple shift-add logic and the look-up table, the proposed approach can reduce the hardware area and improve the conversion speed significantly while achieve similar accuracy compared with the previous methods. The implementation results in both FPGA and 0.18-µm CMOS technology are also presented and discussed.

This paper presents analysis and design of passive RC polyphase filters (RCPFs) in tutorial style. Single-phase model of a single-stage RCPF is derived, and then, multi-stage RCPFs are analyzed and obtained some restrictions for realizable poles and zeros locations of RCPFs. Exact design methods of RCPFs with equal ripple type, and Butterworth type responses are explained for transfer function design and element value design along with some design examples.

In our previous study, we proposed the waveform interpolation (WI) approach to model the excitation signals for hidden Markov model (HMM)-based speech synthesis. This letter presents several techniques to improve excitation modeling within the WI framework. We propose both the time domain and frequency domain zero padding techniques to reduce the spectral distortion inherent in the synthesized excitation signal. Furthermore, we apply non-negative matrix factorization (NMF) to obtain a low-dimensional representation of the excitation signals. From a number of experiments, including a subjective listening test, the proposed method has been found to enhance the performance of the conventional excitation modeling techniques.

OpenFlow, originally proposed for campus and enterprise network experimentation, has become a promising SDN architecture that is considered as a widely-deployable production network node recently. It is, in a consequence, pointed out that OpenFlow cannot scale and replace today's versatile network devices due to its limited scalability and flexibility. In this paper, we propose OpenQFlow, a novel scalable and flexible variant of OpenFlow. OpenQFlow provides a fine-grained flow tracking while flow classification is decoupled from the tracking by separating the inefficiently coupled flow table to three different tables: flow state table, forwarding rule table, and QoS rule table. We also develop a two-tier flow-based QoS framework, derived from our new packet scheduling algorithm, which provides performance guarantee and fairness on both granularity levels of micro- and aggregate-flow at the same time. We have implemented OpenQFlow on an off-the-shelf microTCA chassis equipped with a commodity multicore processor, for which our architecture is suited, to achieve high-performance with carefully engineered software design and optimization.

A large-range switchable RF signal generator is demonstrated using a triple-wavelength fiber laser with uneven-frequency-spacing. Due to the birefringence characteristics of the triple-wavelength fiber laser, switchable dual-wavelength operation can be obtained by adjusting a polarization controller. Therefore, we can achieve a stable RF signals at microwave or millimeter-wave band.

In this letter, we propose a novel precoding scheme for base station (BS) cooperation in downlink cellular networks that allow overlapped clusters. The proposed precoding scheme is designed to mitigate the overlapping-BS interference by maximizing the so-called clustered virtual signal-to-interference-plus-noise ratio (CVSINR). Simulations show that with the proposed scheme, overlapped clustering provides substantial throughput gain over the traditional non-overlapped clustering methods, and user fairness is also improved.

We evaluated the single side-band phase noise of a 40 GHz beat signal generated by two free-running lasers. This allowed us to verify the utility of the two free-running lasers is verified as a light source for a next-generation radio-over-fiber system using frequency such as those in the millimeter-wave and terahertz bands. We also measured the phase noise of a frequency quadrupler using a Mach-Zehnder modulator for comparison. The phase noise of the two free-running lasers and the frequency quadrupler are -63.85 and -95.22 dBc/Hz at a 10 kHz offset frequency, respectively.

We study the role of energy conversion in phase regulation of frequency entrainment. For an open dynamical system that interacts with its environment, energy conversion in the system is the key to a wide variety of nonlinear phenomena including frequency entrainment. In this paper, using the standard notion of energy, we study the phenomena of frequency entrainment by periodic forces in two different types of oscillations: libration and rotation. Theoretical analysis shows a relationship between phase regulation and energy conversion in the entrainment phenomena. Both of them are explained as a common phase regulation. On the other hand, no common relationship between transient behaviors and energy conversion is identified for the two different types of oscillations. For libration, the development of frequency entrainment does not depend on the energy conversion. The energy input to the oscillator affects the amplitude of libration. For the rotation, the development of frequency entrainment is governed by the amount of energy conversion. The energy input to the system directly regulates the phase of rotation, in other words, controls the entrainment phenomenon. These results suggest a different dynamical and control origin behind the two types of entrainment phenomena as the energy conversion in the systems.

High phase noise is a common problem in ring oscillators. Continuous conduction of the transistor in an analog tuning method degrades the phase noise of ring oscillators. In this paper, a digital control tuning which completely switches the transistors on and off, and a 1/f noise reduction technique are employed to reduce the phase noise. A 14-bit control signal is employed to obtain a small frequency step and a wide tuning range. Furthermore, multiphase ring oscillator with a sub-feedback loop topology is used to obtain a stable quadrature outputs with even number of stages and to increase the output frequency. The measured DCO has a frequency tuning range from 554 MHz to 2.405 GHz. The power dissipation is 112 mW from 1.8 V power supply. The phase noise at 4 MHz offset and 2.4 GHz center frequency is -134.82 dBc/Hz. The FoM is -169.9 dBc/Hz which is a 6.3 dB improvement over the previous oscillator design.

To obtain an ultra-short high-intensity pulse source, we investigated the amplification characteristics of two types of pulses (dissipative soliton and stretched pulses) produced by our Yb-doped fiber laser oscillator. Our results show that the dissipative soliton pulse can be amplified with less deterioration than the stretched pulse.

Quasi-phase-matching (QPM) electro-optic modulators using gap-embedded patch-antennas were proposed for improving wireless microwave-optical signal conversion. The proposed QPM devices can receive wireless microwave signals and convert them to optical signals directly. The QPM structures enable us to have twice antenna elements in the fixed device length. The device operations with improved conversion efficiency of 10 dB were experimentally demonstrated at a wireless signal frequency of 26 GHz. The proposed QPM devices were also tested to a wireless-over-fiber link.