In this letter, a 1.25-Gb/s 0.18-µm CMOS half-rate burst-mode clock and data recovery (CDR) circuit is presented. The CDR contains a fast-locking clock recovery circuit (CRC) using a realigned oscillation technique to recover the desired clock. To reduce the power dissipation, the CRC uses a two-stage ring structure and a current-reused concept to merge with an edge detector. The recovered clock has a peak-to-peak jitter of 34.0 ps at 625 MHz and the retimed data has a peak-to-peak jitter of 44.0 ps at 625 Mb/s. The occupied die area of the CDR is 1.41.4 mm2, and power consumption is 32 mW under a 1.8-V supply voltage.

In this paper, we describe a novel focusing mechanism that uses a varifocal mirror and its application to measuring the shape of solder bumps arrayed on an LSI package board based on the shape-from-focus technique. We used a copper-alloy mirror deformed by a piezoelectric actuator as a varifocal mirror to build a simple yet fast focusing mechanism. The varifocal mirror was situated at the focal point of the image-taking lens in image space so that the lateral magnification was constant during focusing and an orthographic projection was perfectly established. The focused plane could be shifted along the optical axis with a precision of 1.4 µm in a depth range of 1.3 mm by driving the varifocal mirror. A magnification of 1.97 was maintained during focusing. Evaluating the curvature of field and removing its effect from the depth data reduced errors. The shapes of 208 solder bumps, 260 µm high and arrayed at a pitch of 500 µm on the board, were measured. The entire 10 mm10 mm board was segmented into 34 partly overlapping sections. We captured 101 images in each section with a high-resolution camera at different focal points at 15 µm intervals. The shape of almost the entire upper hemisphere of a solder bump could be measured. The error in measuring the bump heights was less than 12 µm.

Guiding and nanofocusing of a two-dimensional (2D) optical beam in a negative-dielectric-gap waveguide is studied theoretically. An index-guiding method along the dielectric core embedded in the negative-dielectric-gap is proposed and the confinement properties of the 2D optical beam are studied by the effective-refractive-index method and FDTD simulations. We have shown that the lateral beam width of the 2D optical beam can be shrunk to zero beyond the diffraction limit. A tapered negative-dielectric-gap waveguide using adiabatic propagation achieves nano-focusing and can be applied to nano-optical couplers. This is a gateway from conventional dielectric waveguides to nano-optical integrated circuits.

We investigate the enhancement of the optical nonlinearity and the limit of the improvement of the response speed in CdSxSe1-x microcrystallites by measuring the effective optical nonlinear cross section (σeff), the energy decay time (T1) and the dephasing time in two kinds of semiconductor microcrystallites of CdS0.12Se0.8 microcrystallites embedded in alkaline multi-component glasses (CdSSeMs) and CdSe microcrystallites embedded in SiO2 thin film (CdSeMs). As the average radius of CdSSeMs decreases from 10 to 1 nm, the values of σeff and T1 gradually change from 2.610-16 to 1.110-16 cm2 and from dozens picoseconds to 4 psec, respectively. The size dependence of CdSSEMs shows that the energy level structure in the microcrystallite with a radius of less than a few nanometers is a two-level system, in which σeff is proportional to T2. The carrier recombination time (τ) of CdSSeMs with the average radius of 1 nm is estimated to 2 psec. As the average radius of a CdS0.12Se0.8 microcrystallite decreases from 9 to 3 nm, the values of T2 gradually change from 640 to 230 fsec at 18 K, respectively. The size and temperature dependences of T2 for the CdSSeMs show that there is the discrepancy between the theory and the measured T2. The discrepancy showes the presence of the acoustic-phonon-assisted relaxation processes other than the pure-dephasing processes. It is indicated that T2 becomes long by reducing the excessive acoustic-phonon-assisted relaxation processes, and that the longer T2 might enhance σeff. We investigate the enhancement of σeff in CdSeMs by making T2 longer. The τ, σeff, and T2 of CdSeM an average radius of 3 nm are 40 psec, 4.510-15 cm2, and 150 fsec at room temperature. The σeff is ten times as large as that of CdSSeM sample at the same average radius and the enhancement of σeff can be considered to be caused by the longer T2.

This paper considers a more generalized capacitor that can decrease its width using its own electrical force. We consider a model in which the capacitor with plate distance d is coupled with repulsive mechatronical potential energy, which is proportional to 1/dn. In the conventional case, n is considered to be approximately very large. In our capacitor model, there is a stable point between attractive electrical force and repulsive mechatronical force. In this system, electrostatic energy is equal to the sum of mechatronical potential energy and energy dissipation. Moreover, the mechatronical potential energy is 1/n times smaller than the electrostatic energy. All energies, including the electrostatic energy, potential energy, and energy dissipation, are proportional not to ordinary value V2, but to V2/(n-1)+2, where V is the power supply voltage. This means the voltage dependence of energy is unusual. It is strongly dependent on the capacitor matter, i.e., on the characteristics of the mechatronical system. In addition, the energy dissipation of the system can be reduced to zero using the adiabatic charging process.

This paper proposes a new multi-task synchronization scheme for packet mode orthogonal frequency division multiplexing (OFDM) signals in multi-input multi-output (MIMO) transmission systems; it targets high-rate wireless LANs that offer over 100 Mbit/s. In addition, this paper introduces a packet format for MIMO-OFDM signals that ensures backward compatibility with IEEE 802.11a. The proposed synchronization scheme has simple open-loop construction and consists of automatic frequency control (AFC), symbol timing detection, MIMO channel estimation, and phase tracking. AFC and symbol timing detection are carried out in the time-domain. After OFDM demodulation, the proposed scheme performs MIMO channel estimation and phase tracking in the frequency-domain. Considering all of the above synchronization tasks, we evaluate the packet error rate (PER) performance using the IEEE 802.11 TGn-defined channel model-D and model-E. In channel model-D with the RMS delay spread = 50 ns, the proposed scheme shows superior performance; it suppress the required Eb/N0 degradation to within 0.4 dB with 1000 byte packets compared to the performance achieved if only MIMO channel estimation is considered. Moreover, in channel model-E with the RMS delay spread = 100 ns, it is found that the proposed scheme degrades the required Eb/N0 only by approximately 1.5 dB compared to the MIMO channel estimation only case, even if the packet length is 1000 bytes with 64QAM and coding-rate = 7/8.

In this paper, we propose a modified reproduction strategy of a Genetic Algorithm (GA) utilizing a Self-Organizing Map (SOM) with a novel updating rule of binary weight vectors based on a significance of elements of inputs. In this rule, an updating order of elements is decided by considering fitness values of individuals in a population. The SOM with the proposed updating rule can realize an effective reproduction.

Multilayered network interaction among various networks such as IP/MPLS packet networks and optical fiber networks are now achieved using generalized multiprotocol label switching (GMPLS) technology. One unique feature of GMPLS networks is that GMPLS packet-layer label switching paths (LSPs), such as IP/MPLS LSPs, sometimes tunnel through GMPLS lower layer LSPs such as optical fiber/lambda LSPs. One problem that occurs in this situation is protecting an important primary packet LSP by using a protection LSP that is physically separated from the primary LSP. The packet router has difficulty recognizing lower layer LSPs that are totally disjointed from the primary LSP. This is because, in a GMPLS's packet layer, a source router only differentiates one lower layer LSP from another, and does not check the disjointedness of segments through which the lower layer path passes. Sometimes, different lower LSPs pass through the same optical fiber, and a malfunction of one optical fiber sometimes causes many lower layer LSPs to malfunction at the same time. To solve this problem, a shared risk link group (SRLG) is introduced. Network links that belong to the same SRLG share a common physical resource. We apply this SRLG to the proposed hierarchically distributed path computation elements (HDPCEs) and achieve effective disjointed SRLG protection for important primary GMPLS packet paths.

Parallel programs for distributed memory machines are not easy to create and maintain, especially when they involve sparse matrix computations. In this paper, we propose a program translation system for generating parallel sparse matrix computation codes utilizing PSBLAS. The purpose of the development of the system is to offer the user a convenient way to construct parallel sparse code based on PSBLAS. The system is build up on the idea of bridging the gap between the easy-to-read program representations and highly-tuned parallel executables based on existing parallel sparse matrix computation libraries. The system accepts a MATLAB program with annotations and generates subroutines for an SPMD-style parallel program which runs on distributed-memory machines. Experimental results on parallel machines show that the prototype of our system can generate fairly efficient PSBLAS codes for simple applications such as CG and Bi-CGSTAB programs.

A Non-Uniform Discrete Multitone (DMT) transceiver employing an octave spaced quadrature mirror filter (QMF) bank, can be used to overcome the problem of channel noise enhancement in the zero-forcing (ZF) equalization technique. In this letter, performance of the Non-Uniform DMT system is analyzed. A study of the crosstalk between sub-channels due to non-ideal filter banks is also presented. Crosstalk analysis is based upon the bit error rate (BER) performance versus the QMF order in a standadard ADSL channel. Performance comparison of the Non-Uniform DMT transceiver and a conventional DMT system is given, and it is shown that the Non-Uniform DMT transceiver displays slight improvement over the conventional DMT system for the filters of higher order.

A method of testing distributed amplifiers is presented; multipath interference (MPI) is detected as a beat spectrum between a multipath signal and a direct signal using a frequency-modulated test signal. A test signal with an approximately 450 MHz frequency deviation at an 80 kHz modulation frequency is emitted from a directly modulated DFB-LD by a pulse stream passing through an equalizer. A receiver consisting of a photodiode and an electrical spectrum analyzer (ESA) detects a baseband power spectrum peak appearing at the frequency of the test signal frequency deviation. MPI is converted from the spectrum peak power using a calibration chart. The test method has decreased the minimum detectable MPI as low as -70 dB, compared with that of -50 dB of conventional test methods. The detailed design and performance of the proposed method are discussed, including the calibration procedure, computer simulations for evaluating systematic errors caused by the repetition rate of the frequency modulated test signal and the fiber length under test, and experiments on single-mode fibers and distributed Raman amplifiers.

Adaptation process of retina helps human visual system to see a high dynamic range scene in real world. This paper presents a simple static local adaptation method for high dynamic range image compression based on a retinal model. The proposed simple model aims at recreating the same sensations between the real scene and the range compressed image on display device when viewed after reaching steady state local adaptation respectively. Our new model takes the display adaptation into account in relation to the scene adaptation based on the retinal model. In computing local adaptation, the use of nonlinear edge preserving bilateral filter presents a better tonal rendition in preserving the local contrast and details while avoiding banding artifacts normally seen in local methods. Finally, we demonstrate the effectiveness of the proposed model by estimating the color difference between the recreated image and the target visual image obtained by trial and error method.

A method for evaluating image segmentation methods is proposed in this paper. The method is based on a perception model where the drawing act is used to represent visual mental percepts. Each segmented image is represented by a minimal set of features and the segmentation method is tested against a set of sketches that represent a subset of the original image database, using the Mahalanobis distance function. The covariance matrix is set using a collection of sketches drawn by different users. The different drawings are demonstrated to be consistent across users. This evaluation method can be used to solve the problem of parameter selection in image segmentation, as well as to show the goodness or limitations of the different segmentation algorithms. Different well-known color segmentation algorithms are analyzed with the proposed method and the nature of each one is discussed. This evaluation method is also compared with heuristic functions that serve for the same purpose, showing the importance of using users' pictorial knowledge.

At Eurocrypt'05, Wang et al. presented efficient collision attacks on MD5 and MD4 hash functions. They found a collision of MD5 with a complexity of less than 237 MD5 hash operations, and a collision of MD4 with complexity less than 28 MD4 hash operations. In their attack, the procedure to generate a collision is divided into 4 steps. First, they determine the message differential and output differentials of chaining variables in each step, which generates a collision with small complexity. Second, they construct sufficient conditions that guarantee that the desired differential is always calculated. Third, they find a message modification that can satisfy the sufficient conditions with high probability. Finally, they search for a message that satisfies all sufficient conditions. In this paper, we focus on the message modification of MD5 and MD4, and propose a new message modification. Using our message modification, a collision of MD5 can be found with complexity less than 229 MD5 hash operations, and a collision of MD4 can be found with complexity less than 3 MD4 hash operations. To improve the complexity from previous attacks, we mainly use two ideas. The first idea is to use message modification that can satisfy more sufficient conditions in the second round than in previous attacks. The second idea is to use message modification that can enable us to search for a collision starting from an intermediate step.

This letter proposes a simple and efficient random-binning based distributed source coding (DSC) scheme for application to remote source estimation in wireless sensor networks. The scheme jointly encodes data from multiple sensors with side information. It achieves high coding efficiency and reduces power and bandwidth consumption.

This paper presents a fast elemental image generation algorithm, called the Viewpoint Vector Rendering (VVR), for the computer-generated integral imaging system. VVR produces a set of elemental images in real-time by assembling the segmented area of the directional scenes taken from a range of viewpoints. This algorithm is less affected by system factors such as the number of elemental lens and the number of polygons. It also supports all display modes of the integral imaging system, real, virtual and focused mode. This paper first describes the characteristics of integral imaging system. It then discusses the design, implementation, and performance evaluation of the VVR algorithm, which can be easily adapted to render the integral images of complex 3D objects.

We present the use of a Modified Generalized Hough Transform (MGHT) and deformable contours for image data retrieval where a given contour, gray-scale, or color template image can be detected in the target image, irrespective of its position, size, rotation, and smooth deformation transformations. Potential template positions are found in the target image using our novel modified Generalized Hough Transform method that takes measurements from the template features by extending a line from each edge contour point in its gradient direction to the other end of the object. The gradient difference is used to create a relationship with the orientation and length of this line segment. Potential matching positions in the target image are then searched by also extending a line from each target edge point to another end along the normal, then looking up the measurements data from the template image. Positions with high votes become candidate positions. Each candidate position is used to find a match by allowing the template to undergo a contour transformation. The deformed template contour is matched with the target by measuring the similarity in contour tangent direction and the smoothness of the matching vector. The deformation parameters are then updated via a Bayesian algorithm to find the best match. To avoid getting stuck in a local minimum solution, a novel coarse-and-fine model for contour matching is included. Results are presented for real images of several kinds including bin picking and fingerprint identification.

We propose a new construct, the Text-Graphics Character (TGC) CAPTCHA, for preventing dictionary attacks against password authentication systems allowing remote access via dumb terminals. Password authentication is commonly used for computer access control. But password authentication systems are prone to dictionary attacks, in which attackers repeatedly attempt to gain access using the entries in a list of frequently-used passwords. CAPTCHAs (Completely Automated Public Turing tests to tell Computers and Humans Apart) are currently being used to prevent automated "bots" from registering for email accounts. They have also been suggested as a means for preventing dictionary attacks. However, current CAPTCHAs are unsuitable for text-based remote access. TGC CAPTCHAs fill this gap. In this paper, we define two TGC CAPTCHAs and incorporate one of them in a prototype based on the SSH (Secure Shell) protocol suite. We also prove that, if a TGC CAPTCHA is easy for humans and hard for machines, then the resulting CAPTCHA is secure. We provide empirical evidence that our TGC CAPTCHAs are indeed easy for humans and hard for machines through a series of experiments. We believe that a system exploiting a TGC CAPTCHA will not only help improve the security of servers allowing remote terminal access, but also encourage a healthy spirit of competition in the fields of pattern recognition, computer graphics, and psychology.

A waveguide-based surface plasmon resonance (SPR) sensor with an adsorbed layer is analyzed using the beam-propagation method. For two-dimensional (2-D) models, numerical results show that the change in thickness of the adsorbed layer placed on the metal leads to a significant shift of the maximum absorption wavelength. Through eigenmode analysis, the maximum absorption wavelength is found to be consistent with the cutoff wavelength of the second-order surface plasmon mode. The designed 2-D sensor shows an absorption wavelength shift from 0.595 to 0.603 µm, when the analyte refractive index is increased from 1.330 to 1.334. After a basic investigation using the 2-D models, we next study 3-D models. When the metal with the absorbed layer is wide enough to cover the core region, the 3-D results are similar to the 2-D results. However, as the metal width is reduced, the absorption wavelength shifts toward a shorter wavelength and the sensitivity to the refractive index change degrades gradually. The degradation of the sensitivity is considerable when the metal width is narrower than the core width. As a result, the metal width of the practical SPR sensor should be slightly wider than the core width so as to maintain the sensitivity corresponding to that obtained for the 2-D model.

Energy-saving is crucial in wireless sensor networks. In this letter, we address the issue of lossless packing aggregation with the aim of reducing energy lost in cluster-model wireless sensor networks. We propose a performance model based on the bin packing problem to study the packing efficiency. It is evaluated in terms of control header size, and validated by simulations.