With the rapid increase in recording density in recent years, the development of media with high coercivity and low noise has become an important issue in perpendicular as well as longitudinal recording. Compared with the CoCr binary system, the CoCrTa system is more effective in increasing coercivity. The increase in coercivity is due to not Ta segregation but to enhanced Cr segregation at column boundaries caused by Ta addition. When a Ti underlayer with uniform thickness was used, there was no improvement in c-axis alignment of the magnetic layers in CoCrTa and CoCrPt films, although the lattice mismatch of Co ternary alloys with Ti was much reduced compared with that of the CoCr film with Ti. This indicates that there may be no direct heteroepitaxial relationship between Ti underlayer and CoCr alloys at the Ti-Co alloy interface. In the case of the CoCrPt film, perpendicular coercivity increased linearly as Pt content increased up to 10at%. When Pt content was about 13at%, the shape of the M-H loop showed characteristics of domain wall motion reversal, which indicated strong exchange coupling among columns. When Ta content was increased to 4at% in the CoCrPt film, perpendicular coercivity increased and the shape of the M-H loop suggested that the domain wall motion reversal behavior was much reduced. This is thought to be associated with Cr segregation at column boundaries by Ta addition.

A punctured convolutional coded PR4ML system for digital magnetic recording, which applies a punctured coding method to the convolutional code and records the punctured code sequences on two tracks, is proposed. In this study, the bit error rate performance of the proposed system is obtained by computer simulation taking account of partial erasure, which is one of the nonlinear distortions at high densities, and it is compared with those of a conventional 8/9 coded PR4ML system and an I-NRZI coded PR4ML system. The results show that the proposed system is hardly affected by partial erasure and exhibits good performance in high-density recording. A bit error rate of 10-4 can be achieved with SNR's of approximately 13.2 dB and 9.1 dB less than those of the conventional 8/9 coded and I-NRZI coded PR4ML systems, respectively, at a normalized linear density of 3.

Time decay of magnetic properties in perpendicular magnetic recording media was studied. It was suggested that magnetization in media with a low energy ratio, KV/kT, of 50 is thermally stable in the absence of a demagnetizing field while coercivity exhibits a large time dependence. Magnetization in perpendicular recording media exhibited an appreciable time decay even for films with a large energy ratio of 300. The decay is attributed to the small perpendicular squareness due to a large perpendicular demagnetizing field acting in the media. The recording density dependence of the time decay in the output was explained in terms of the change in the demagnetizing field with the density. It is concluded that the use of media with large squareness as well as large energy ratio effectively reduces time decay in the output.

Recently, the spatio-temporal filter using linear analog Cellular Neural Network (CNN), called CNN filter array, has been proposed for the purpose of dynamic image processing. In this paper, we propose a design method of descrete-time cellular neural network filter which selectively extracts the particular moving object from other moving objects and noise. The CNN filter array forms a spatio-temporal filter by arranging cells with a same function. Each of these cells is a simple linear analog temporal filter whose input is the weighted sum of its neighborhood inputs and outputs and each cell corresponds to each pixel. The CNN filter is formed by new model of discrete time CNN, and the filter parameters are determined by applying backpropagation algorithm in place of the analytic method. Since the number of connections between neurons in the CNN-type filter is relatively few, the required computation in the learning phase is reasonable amount. Further, the output S/N ratio is improved by introducing nonlinear element. That is, if the ratio of output to imput is smaller than a certain value, the output signal is treated as a noise signal and ought to be rejected. Through some examples, it is shown that the target object is enhanced in the noisy environment.

Several types of transmission-line coupling are analyzed to use in one- and two-dimensional active antenna arrays, and a method is developed to scan the beam of the arrays using the mutual locking theory. To compensate the undesired effect of strong radiative coupling of the nearest neighbor elements on the phased array performance, addition of resistive stubs to the end elements is proposed. In a 14 array it was observed that after the connection of resistive stubs, the scanning range of the array increased considerably. The effect of oscillator amplitudes on the phased array behavior is explored numerically. In the experiments main beam of 22 and 33 active antenna arrays were steered up to 25 and 15, respectively in the H-plane.

In this paper, we propose a new switching network architecture with output queueing, The proposed switch, FBSF (FAB Banyan Switching Fabrics) can deliver up to 2r packets simultaneously destined for the same outlet in a single time slot. The switch fabrics consist of Batcher sorter, a radix-r double shuffle network r-packet distributors, two FAB networks, and output buffer modules. The performance of the switch fabric is evaluated by measures of throughput, average queue length, average waiting time, and packet loss rate. Numerical and simulation results indicate that the switch exhibits very good delay-throughput performance over a wide range of input traffic.

This paper first proposes a new approach to designing high-quality, low-diameter, small mean-internode-distance (MID), k-subcubic-connected cyclic networks. The approach is a modification of the k-cubic-connected cyclic (k-ccc) network in which there are N=k2k-1 instead of N=k2k nodes in the k-ccc network. The special features of this network are: (1) It fills the gap between the number of nodes in k-ccc and (k+1)-ccc networks, but retains a constant number of link (3) per node in the network, (2) it allows higher quality, smaller diameters and mean internode distances hypercube networks with the same numbers of nodes. A second novel approach consists of a k+-sccc network with the same number of nodes as the k-ccc but with smaller diameters and mean internode distances. A generalized k-ccc network formed by nodes N=k2m is introduced for n-cube and k-ccc (modified or normal) networks that allows minimum network quality to be obtained where m may or may not equal to k. A routing algorithm for 4-sccc is also presented.

Linear programming techniques are useful in many diverse applications such as: production planning, energy distribution etc. To find an optimal solution of the linear programming problem, we have to repeat computations and it takes a lot of processing time. For high speed computation of linear programming, special purpose hardware has been sought. This paper proposes a systolic array for solving linear programming problems using the revised simplex method which is a typical algorithm of linear programming. This paper also proposes a modified systolic array that can solve linear programming problems whose sizes are very large.

The multipass rendering method based on the global illumination model can generate the most photo-realistic images. However, since the multipass rendering method is very time consuming, it is impractical in the industrial world. This paper discusses a massively parallel processing approach to fast image synthesis by the multipass rendering method. Especially, we focus on the performance evaluation of the view-dependent object-space parallel processing on the (Mπ)2 which has been proposed in our previous paper. We also propose two kinds of distributed frame buffer system named cached frame buffer and multistage-interconnected frame buffer. These frame buffer systems can solve the access conflict problem on the frame buffer. The simulation results show that the (Mπ)2 has a scalable performance. For example, the (Mπ)2 with more than 4000 processing elements can achieve an efficiency of over 50%. We also show that both of the proposed distributed frame buffer systems can relieve the overhead due to frame buffer access in the (Mπ)2 in the case that a large number of high-performance processing elements are adopted in the system.

For the solutions of linear systems of equations with unsymmetric coefficient matrices, we propose an improved version of the quasi-minimal residual (IQMR) method by using the Lanczos process as a major component combining elements of numerical stability and parallel algorithm design. For Lanczos process, stability is obtained by a coupled two-term procedure that generates Lanczos vectors scaled to unit length. The algorithm is derived such that all inner products and matrixvector multiplications of a single iteration step are independent and communication time required for inner product can be overlapped efficiently with computation time. Therefore, the cost of global communication on parallel distributed memory computers can be significantly reduced. The resulting IQMR algorithm maintains the favorable properties of the Lanczos process while not increasing computational costs. The efficiency of this method is demonstrated by numerical experimental results carried out on a massively parallel distributed memory computer, the Parsytec GC/PowerPlus.

We present a scalable parallel memory architecture with a skew scheme by which permanent-concentration-free strides, if any, do not depend on the number of ways in parallel memory interleaving. The permanent-concentration is a kind of memory access conflict. With conventional skew schemes, permanent-concentration-free strides depended on the number of banks (or bank groups) in parallel memory (=number of ways in parallel memory interleaving). We analyze two kinds of cause of conflicts: permanent-concentration occurs when memory access requests concentrate in limited number of banks (or bank groups) in parallel memory, and transient-concentration, when memory access requests transiently concentrate in some banks (or bank groups) in parallel memory. We have identified permanent-concentration-free strides, which are independent of the number of banks (or bank groups) in parallel memory, by solving two concentrations separately. The strategy is to increase the size of address block of shifting address assignment to the parallel memory in order to reduce permanent-concentrations, and make the size of the buffer for each banks (or bank groups) in the parallel memory match the size of address block of shifting in order to absorb transient-concentrations. The skew scheme uses the same size of address block of shifting address assignment for memory systems for different numbers of banks (or bank groups) in parallel memory. As a result, scalability for permanent-concentration-free strides is achieved independent of the number of banks (or bank groups) in parallel memory.

Let L be any class of languages, L' be one of the classes of context-free, context-sensitive and recursively enumerable languages, and Σ be any alphabet. In this paper, we show that if the following statement (1) holds, then the statement (2) holds. (1) For any language L in L over Σ, there exist an alphabet Γ including Σ, a homomorphism h:Γ*Σ* defined by h(a)=a for aΣ and h(a)=λ (empty word) for aΓ-Σ, a Dyck language D over Γ, and a language L1 in L' over Γ such that L=h(DL1). (2) For any language L in L over Σ, there exist an alphabet of k pairs of matching parentheses Xk, Dyck reduction Red over Xk, and a language L2 in L' over ΣXk such that L=Red(L2)Σ*. We also give an application of this result.

The finite reconfigurability and local reconfigurability of graphs were proposed by Sha and Steiglitz [1], [2] in connection with a problem of on-line reconfiguraion of WSI networks for run-time faults. It is shown in [2] that a t-locally-reconfigurable graph for a 2-dimensional N-vertex array AN can be constructed from AN by adding O(N) vertices and edges. We show that Ω(N) vertices must be added to an N-vertex graph GN in order to construct a t-locally-reconfigurable graph for GN, which means that the number of added vertices for the above mentioned t-locally-reconfigurable graph for AN is optimal to within a constant factor. We also show that a t-finitely-reconfigurable graph for an N-vertex graph GN can be constructed from GN by adding t vertices and tN + t (t+1)/2 edges.

In this paper, a new bits truncation adaptive pyramid (BTAP) algorithm for motion estimation is presented. The method employs bits truncation of the gray level from 8bits to much less bits in the searching algorithm. Compared with conventional fast block matching algorithms, this method drastically improves speed for motion estimation of reduced gray-level images and preserves reasonable performance and algorithm reliability. Bits truncation concept is well combined with hierarchical pyramid algorithm in order to truncate adaptively according to image characteristics. The computation complexity is much less than that of pyramid algorithm and 3-Step motion estimation algorithm because of bit-truncated searbh and low overhead adaptation. Nevertheless, the PSNR property is also comparable with these two algorithms for various video sequences.

We previously proposed a robust hybrid edge detector which relaxes the trade off between robustess against noise and accurate localization of the edges. This hybrid detector separates the tasks of localization and noise suppresion between two sub-detectors. In this paper, we present an extension to this hybrid detector to determine its optimal parameters, independently of the scene. This extension defines a probabilistic cost function using for criteria the probability of missing an edge buried in noise and the probability of detecting false edges. The optimization of this cost function allows the automatic selection of the parameters of the hybrid edge detector given the height of the minimum edge to be detected and the variance of the noise, σ2n. The results were applied to the 2D case and the performance of the adaptive hybrid detector was compared to other detectors.

UNcorrectable Bit Errors (UNBEs) are important in considering the reliability of Redundant Array of Inexpensive Disks (RAID). They, however, have been ignored or have not been studied in detail in existing reliability analysis of RAID. In this paper, we present an analytic model to study the reliability of declustered-parity RAID by considering UNBEs. By using the analytic model, the optimistic and the pessimistic estimates of the probability that data loss occurs due to an UNBE during the data reconstruction after a disk failed (we call this DB data loss) are obtained. Then, the optimistic and the pessimistic estimates of the Mean Time To Data Loss (MTTDL) that take into account both DB data loss and the data loss caused by double independent disk failures (we call this DD data loss) are obtained. Furthermore, how the MTTDL depends on the number of units in a parity stripe, rebuild time of a failed disk and write fraction of data access are studied by numerical analysis.

Detailed investigations of the microstructural properties of SrGa2S4:Ce3+ thin films grown by deposition from binary vapors (DBV) were carried out by X-ray diffraction analysis (XRD), energy dispersive X-ray diffraction measurements (EDX), electron probe microanalysis (EPMA), and X-ray photoelectron spectroscopy (XPS) depth profiling. The results indicate uniform distribution of the constituent elements in the nearly stoichiometric structure of the thin films. Photoluminescence (PL) data including absorption and luminescence spectra in the temperature range of 10 to 300 K and decay characteristics show that an increase in Ce concentration from 0.2 to 3 mol% is accompanied with a marked increase in both the intensity of activator absorption and decay time, while the emission and excitation bands remain fixed in position. A mechanism involving the concentration-dependent interactions between different centers in the lattice is proposed, which may explain the experimentally observed behavior.

Obradovic and Parberry showed that any n-input k-ary function can be computed by a depth 4 unit-weight k-ary threshold circuit of size O(nkn). They also showed that any n-input k-ary symmetric function can be computed by a depth 6 unit-weight k-ary threshold circuit of size O(nk+1). In this paper, we improve upon and expand their results. The k-ary threshold circuits of nonunit weight and unit weight are considered. We show that any n-input k-ary function can be computed by a depth 2 k-ary threshold circuit of size O(kn-1). This means that depth 2 is optimal for computing some k-ary functions (e.g., a PARITY function). We also show that any n-input k-ary function can be computed by a depth 3 unit-weight k-ary threshold circuit of size O(kn). Next, we show that any n-input k-ary symmetric function can be computed by a depth 3 k-ary threshold circuit of size O(nk-1), and can be computed by a depth 3 unit-weight k-ary threshold circuit of size O(knk-1). Finally, we show that if the weights of the circuit are polynomially bounded, some k-ary symmetric functions cannot be computed by any depth 2 k-ary threshold circuit of polynomial-size.

This paper presents a clock routing technique called Balanced-Mesh Method (BMM) which incorporates the advantages of two famous conventional-clock-routing techniques. One is the balanced-tree method (BTM) where the clock net is routed as a tree so that the delay times of clock signal are balanced, and the other is the fixed-mesh method (FMM) where the clock net is routed as a fixed mesh driven by a large buffer. In BMM, the clock net is routed as a set of relatively small meshes of interconnects driven by relatively small buffers. Each mesh covers an area called a Mesh-Routing Region (MR) in which its delay and skew can be suppressed within a certain range. These small meshes are connected by a balanced tree with the chip clock source as its root. To implement BMM, we developed an MR-partitioning program that partitions the circuit into MR's according to a set of pre-determined constraints on the number of flip-flops and the area in each MR, and a clock-global-routing program that provides each mesh routing and the tree routing connecting meshes. We applied BMM to the design of an MPEG2-encoder LSI and achieved a skew of 210ps. In addition, the experimental results show BMM yields the lowest power dissipation compared to conventional methods.

In this paper, we prove that for a class of nonsymmetric neural networks with connection matrices T having nonnegative off-diagonal entries, -T is an M-matrix is a necessary and sufficient condition for absolute exponential stability of the network belonging to this class. While this result extends the existing one of absolute stability in Forti, et al., its proof given in this paper is simpler, which is completed by an approach different from one used in Forti, et al. The most significant consequence is that the class of nonsymmetric neural networks with connection matrices T satisfying -T is an M-matrix is the largest class of nonsymmetric neural networks that can be employed for embedding and solving optimization problem with global exponential rate of convergence to the optimal solution and without the risk of spurious responses. An illustrating numerical example is also given.