We propose an asymmetric fragile watermarking technique that uses a number theoretic transform (NTT). Signature data is extracted from a watermarked image by determining correlation functions that are computed using the NTT. The effectiveness of the proposed method is evaluated by simulated detection of altering.

The use of the Constructive Solid Geometry (CSG) model has been considered in several computer-aided design systems for recent years, since its concept of powerful and multiple operations on basic object shapes to create more complex ones is intuitively easy to understand. Based on the CSG concept and a guiding principle of scene analysis, an algorithm for interpreting three-view drawings is described in this paper. In a certain process, the 3D interpretation works on local recognition to detect possible subparts of which orthographic patterns are defined in the 2D description of a part. In the subsequent process, which examines all possible solutions to the given drawing until finding one that meets some goal criteria, the combinatorial operators are applied to the possible subparts. Through those repeated processes, the final solution can be obtained in terms of consistent subparts in a CSG tree, including additional information about solids and cavities.

A Josephson parametric oscillator (JPO) is an interesting system from the viewpoint of quantum optics because it has two stable self-oscillating states and can deterministically generate quantum cat states. A theoretical proposal has been made to operate a network of multiple JPOs as a quantum annealer, which can solve adiabatically combinatorial optimization problems at high speed. Proof-of-concept experiments have been actively conducted for application to quantum computations. This article provides a review of the mechanism of JPOs and their application as a quantum annealer.

Design and evaluation of a high-performance switch architecture for free-space photonic switching systems is described. The switch is constructed of 22 switching elements and employs special multistage interconnection patterns. The connection setup algorithm and the control procedure at the switching elements are based on a "rerouting algorithm." Performance analysis shows that the blocking probability of the switch is easily controlled by increasing the number of switching stages. Example implementations of this switch are shown in which birefringent plates, polarization controllers, etc. are used.

Laser module fabricated with silicon platform technology is very attractive for low-cost modules. The technology enables passive optical alignment of an LD to an optical fiber. Our marker design for passive alignment allows positioning accuracy within 1 µm of LD. However, coupling efficiency is a key issue because that by conventional butt coupling scheme is low with about 10 dB coupling loss. We investigated optical coupling characteristics in various types of coupling scheme: conventional flat end fibers, cone fibers, integrated GRIN rod lenses on the platform and the coupling with new-type LDs integrated with spot size transformer. Improvement of coupling efficiency with 3 dB and 7.5 dB compared to flat-end fiber is achieved by using the cone fiber and the GRIN rod lens, respectively, although 1-dB coupling tolerances for alignment deteriorated with these schemes. We obtained high efficient coupling with 3.5 dB coupling loss and wide alignment tolerance of 2.3 µm simultaneously with a new-type LD integrated with spot size transformer owing to its expanded spot size characteristics.

Voxel representation of solid object is a well known model that is widely used in CAD, robots, computer graphics, and medical image processing. Efficient algorithms for the tracing in voxel model are of great importance. A fast hardware oriented voxel tracing algorithm (called LCDDA) is proposed and implemented. All the voxels pierced by a given ray are generated incrementaly. To meve from a voxel to the next one only three fixed point additions and comparisons, which can be done using 3 parallel pipelines, and a ROM access are required. It takes 0.2 microseconds to do this under 5 MHz clock on a personal computer, which is 103 times faster than Fujimoto's and 1339 times than Glassner's algorithm on a workstation. As an application of this, time consuming ray tracing process is performed by this hardware implemented algorithm on a personal computer. Also, an active intersection table (AIT) is introduced to avoid multiple intersection of a ray and the same object. The high speed of these methods have been proved by experimental results.

Speech quality of VoIP (Voice over Internet Protocol) may potentially be degraded by transmission errors such as packet loss and delay that are basically inevitable in best-effort communications. This study newly proposes an error concealment technique for such degradation by taking account of both sender-based and receiver-based techniques. In the proposed technique, sender-based side information, which is required by the receiver-based technique, is transmitted by using steganography, so that its datagram is completely compatible with the conventional format of VoIP. From experimental results of objective evaluation, it is indicated that the proposed technique may potentially be useful for improvement of speech quality, compared with the conventional technique.

Expansive graph grammar is one of the suitable tools for describing pattern structures in syntactic pattern recognition. To describe the numerical features of patterns and relations among them simultaniously with pattern structure, in this paper we show with expansive graph grammar: (1) how to describe the dependent relations among attributes of (sub) patterns with the concepts of inherited and synthesized attributes, (2) how to describe conditions supposed to be satisfied by attributes of patterns with the concept of predicate. An interpreter for such processing is presented based on the Problem-Reduction Representation (PRR). Some features of the method and the interpreter are discussed. It is showed that the method introduced in this paper is suitable for describing patterns in scene analysis when numerical features of patterns are considered.

We propose new lossless medical image compression method based on hierarchical sorting technique. Hierarchical sorting is a technique to achieve high compression ratio by detecting the regions where image pattern varies abruptly and sorting pixel order by its value to increase predictability. In this method, we can control sorting accuracy along with size and complexity. As the result, we can reduce the sizes of the permutation-tables and reuse the tables to other image regions. Comparison using experimental implementation of this method shows better performance for medical image set measured by X-ray CT and MRI instruments where similar sub-block patterns appear frequently. This technique applies quad-tree division method to divide an image to blocks in order to support progressive decoding and fast preview of large images.

We have measured the temperature dependence of the gain characteristics in 1.3-µm AlGaInAs/InP strained multiple-quantum-well (MQW) semiconductor lasers using Hakki-Paoli method. By measuring the temperature dependences of the peak gain value and the gain peak wavelength, we evaluated the temperature dependences of the threshold current and the oscillation wavelength, respectively. The small temperature dependence of the threshold current in AlGaInAs/InP lasers is caused by the small temperature dependence of the transparency current density, which is represented by the characteristic temperature TJtr of 116 K. In AlGaInAs/InP high T0 lasers, the temperature dependence of the oscillation wavelength is slightly larger than that in GaInAsP/InP lasers because of the larger temperature dependence of bandgap wavelength 0.55 nm/K.

Controlling fluid simulation is one of the important research topics in computer graphics. In this paper, we focus on controlling the simulation of cumuliform cloud formation. Using a previously proposed method for controlling cloud simulation the convergence speed is very slow; therefore, it takes a long time before the clouds form the desired shapes. We improved the method and accelerated the convergence by introducing a new mechanism for controlling the amount of water vapor added. We demonstrate the effectiveness of the proposed method by several examples.

We have measured the temperature dependence of the gain characteristics in 1.3-µm AlGaInAs/InP strained multiple-quantum-well (MQW) semiconductor lasers using Hakki-Paoli method. By measuring the temperature dependences of the peak gain value and the gain peak wavelength, we evaluated the temperature dependences of the threshold current and the oscillation wavelength, respectively. The small temperature dependence of the threshold current in AlGaInAs/InP lasers is caused by the small temperature dependence of the transparency current density, which is represented by the characteristic temperature TJtr of 116 K. In AlGaInAs/InP high T0 lasers, the temperature dependence of the oscillation wavelength is slightly larger than that in GaInAsP/InP lasers because of the larger temperature dependence of bandgap wavelength 0.55 nm/K.

We have developed membrane distributed Bragg reflector (DBR) lasers on thermally oxidized Si substrate (SiO2/Si substrate) to evaluate the parameters of the on-Si lasers we have been developing. The lasers have InGaAsP-based multi-quantum wells (MQWs) grown on InP substrate. We used direct bonding to transfer this active epitaxial layer to SiO2/Si substrate, followed by epitaxial growth of InP to fabricate a buried-heterostructure (BH) on Si. The lateral p-i-n structure was formed by thermal diffusion of Zn and ion implantation of Si. For the purpose of evaluating laser parameters such as internal quantum efficiency and internal loss, we fabricated long-cavity lasers that have 200- to 600-µm-long active regions. The fabricated DBR lasers exhibit threshold currents of 1.7, 2.1, 2.8, and 3.7mA for active-region lengths of 200, 300, 400, and 600µm, respectively. The differential quantum efficiency also depends on active-region length. In addition, the laser characteristics depend on the distance between active region and p-doped region. We evaluated the internal loss to be 10.2cm-1 and internal quantum efficiency to be 32.4% with appropriate doping profile.

Design and evaluation of a high-performance switch architecture for free-space photonic switching systems is described. The switch is constructed of 22 switching elements and employs special multistage interconnection patterns. The connection setup algorithm and the control procedure at the switching elements are based on a "rerouting algorithm."" Performance analysis shows that the blocking probability of the switch is easily controlled by increasing the number of switching stages. Example implementations of this switch are shown in which birefringent plates, polarization controllers, etc. are used.

We present an algorithm for efficient rendering of animated hair under a dynamic, low-frequency lighting environment. We use spherical harmonics (SH) to represent the environmental light. The transmittances between a point on a hair strand and the light sources are also represented by SH functions. Then, a convolution of SH functions and the scattering function of a hair strand is precomputed. This allows us to efficiently compute the intensity at a point on the hair. However, the computation of the transmittance is very time-consuming. We address this problem by using a voxel-based approach: the transmittance is computed by using a voxelized hair model. We further accelerate the computation by sampling the voxels. By using our method, we can render a hair model consisting of tens of thousands of hair strands at interactive frame rates.

This paper describes an experimental system for designing three-dimensional solid objects through three-view orthographic drawings, using automatic three-dimensional interpretation in cooperating with a set of interactive drawing-oriented design utilities. In the design process based on the system approach, an object is viewed as being consisting of several volumetric instances, each of which is further composed a number of simple subvolumes. In the system, whereas the automatic interpretation is employed to construct the instances from their orthographic projections, the design utilities are provided to allow modifications of a solid-object model being composed of the constructed instances. Once a solid-object model is created from a drawing containing the projections of an instance, modifications on the drawing can be performed for addition of new instances into the existing solid-object model, and changes and deletion of the instances existing in the model. Being aimed at a two-dimensional interface for the Constructive Solid Geometry, or CSG method, the system provides the user with design interaction procedures which let the user manipulate the projections of the instances in terms of two-dimensional graphical primitives, such as straight lines, arcs, and circles, obtain and display a solid object constructed from the projections being designed. In addition, more complex three-dimensional object shapes can be achieved using this alternative approach after the interpretation concept.

We have proposed a novel concept of a digital watermarking technique for music data that focuses on the use of sound synthesis and sound effect techniques. This paper describes the details of our proposed technique that employs the distortion effect, one of the most common sound effects frequently utilized especially for guitar and bass instruments. This paper describes the experimental results of evaluating the resistance of the proposed technique against some basic malicious attacks utilizing MP3 coding, tempo alteration, pitch alteration, and high-pass filtering. It is demonstrated that the proposed technique potentially has appropriate resistance against such attacks except for the high-pass filtering attack. A technique for increasing the resistance against the high-pass filtering attack is also supplementarily discussed.

This letter describes our DFB-LD module for use in WDM optical access networks. We realized an isolator-free DFB-LD module with a thermo-electric cooler in aim of stabilizing the emission wavelength for WDM systems. Silicon waferboard technology was employed to achieve simple assembly and small size of the module. This small size contributed to low TEC power. Our fabricated module demonstrated low-noise and stable emission wavelength characteristics under 156 Mbit/s pseudo random modulation.

We describe an algorithm for efficiently compositing partial images generated during parallel volume rendering on a distributed memory parallel computer. In this object space partitioning algorithm, each PE is assigned to several subvolumes where each subvolume has a corresponding local frame buffer. After volume rendering is performed independently for each subvolume, the partial images stored in the local frame buffers are combined to generate a complete image. During this compositing process, the communication of partial image data between the PEs is kept minimal by assigning PEs to subvolumes in an interleaved manner. This assignment makes possible a reduction in communication in the axis direction in which there is the most communication. Experimental results indicate that a 9% to 35% reduction in the total rendering time can be attained with no additional data structures and no memory overhead.

To employ Computer Graphics (CG) technology in the production of CG holograms or similar applications where the generation of consecutive pictures with rotated viewing directions is demanded takes a lot of time and money. This paper presents a two-pass surface rendering method for fast creating such animated pictures from a single view image structure. Instead of generating display data for a single picture, the first pass program constructs a Position Oriented (PO) frame buffer that contains the information of control points on every order of visible surfaces. A display program of second pass manipulates the frame buffer structure to generate surface rendered pictures with spatial and perspective transforms. Experiments proved the method is effective to create high quality surface rendered images with rotation capability. Various usuful facilities for CAD visualization have also been developed within the technique. The improvements on memory consumption and picture quality are also discussed in this paper.