We have achieved the room temperature cw lasing operation of GaInAsP/InP surface emitting lasers for the first time. By employing a buried heterostructure with 1.3 µm range active region and a MgO/Si heat sink mirror, cw operation was obtained up to 14 with the threshold current of 22 mA.

A new method by which images are coded with predictable and controllable subjective picture quality in the minimum cost of bit rate is developed. By using wavelet transform, the original image is decomposed into a set of subimages with different frequency channels and resolutions. By utilizing human contrast sensitivity, each decomposed subimage is treated according to its contribution to the total visual quality and to the bit rate. A relationship between physical errors (mainly quantization errors) incurred in the orthonormal wavelet image coding system and the subjective picture quality quantified as the mean opinion score (MOS) is established. Instred of using the traditional optimum bit allocation scheme which minimizes a distortion cost function under the constraint of a given bit rate, we develop an "optimum visually weighted noise power allocation" (OVNA) scheme which emphasizes the satisfying of a desired subjective picture quality in the minumum cost of bit rate. The proposed method enables us to predict and control the picture quality before the reconstruction and to compress images with desired subjective picture quality in the minimum bit rate.

A quantum interconnection scheme by controlling the Coulomb interaction between ballistic electrons is proposed in which 2DEG (2 dimensional electron gas) plays the role of an interconnection medium. This concept brings up new possibilities for the interconnection approach in various fields such as parallel processing, telecommunications switching, and quantum functional devices. Cross-over interconnection, address collision, and address selection in a quantum information network system were analyzed as the first step. The obtained results have shown that the interconnection probability can be controlled by the velocity and timing of the ballistic electron emission from the emitter electrode. The proposed interconnection scheme is expected to open up a new field of quantum effect integrated circuits in the 21st century.

A linear block code has a finite-length trellis diagram which terminates at the length of the code. Such a trellis diagram is expressed and constructed in terms of sections. The complexity of an L-section trellis diagram for a linear block code is measured by the state and branch complexities, the state connectivity, and the parallel structure. The state complexity is defined as the number of states at the end of each section of the L-section trellis diagram, the branch complexity is defined as the number of parallel branches between two adjacent states, the state connectivity is defined in terms of the number of states which are adjacent to and from a given state and the connections between disjoint subsets of states, and the parallel structure is expressed in terms of the number of parallel sub-trellis diagrams without cross connections between them. This paper investigates the branch complexity, the state connectivity, and the parallel structure of an L-section minimal trellis diagram for a binary linear block code. First these complexities and structure are expressed in terms of the dimensions of specific subcodes of the given code. Then, the complexities of 2i-section minimal trellis diagrams for Reed-Muller codes are given.

A fiber-optic transmission system for linking radio base stations to the mobile communication center is developed, and its performance is evaluated. The introduction of this system yields two main improvements: optimum zone allocation to increase radio frequency utilization efficiency and the elimination of service quality issues such as dead zones and traffic imbalance. Being optical, the system suffers from the interferometric noise and distortion created by multiple reflections within the fiber. Moreover, because system response is much different from that of optical CATV systems, we clarify the optical parameter selection criteria and hypothetical return loss model for an embedded fiber infrastructure. An optical multiplexing method is also introduced that reduces the quantity of fiber and connectors, as well as splicing and cable installation costs. A new ternary optical multiplexing architecture combined with a cost-effective self-tuning type WDM technique and a high isolation type circulator are proposed for the 1.3µm wavelength region. The performance of low distortion high power common amplifiers is measured with the aim of reducing the size and weight of back-up batteries, and to improve the packaging density of the typical base station.

System and chip synthesis must evaluate candidate Register-Transfer (RT) architectures with respect to finished physical designs. Current RT level cost measures, however, are highly simplified and do not reflect the real physical disign. Complete physical design, on the other hand, is quite costly, and infeasible to be iterated many times. In order to establish a more realistic assessment of layout effects, we propose a new layout model which efficiently accounts for the effects of wiring and floorplanning on the area and performance of RT level designs, before the physical design process. Benchmarking has shown that our model is quite accurate.

Acceleration techniques have been incorporated into the generalized method of characteristics (GMC) to perform transient analysis of uniform transmission lines, for the special case when the transmission lines are driven by digital signals. These techinques have been proved to improve the simulation speed to a great extent when the analysis is carried out using iterative waveform relaxation method. It has been identified that the load impedance connected to the transmission line has a bearing on the efficiency of one of these acceleration techniques. Examples of an RLCG line terminated with linear loads as well as nonlinear loads are given to illustrate the advantage of incorporating these acceleration techniques.

Logic synthesizers usually have good area minimization capabilities, producing circuits of minimal area. But good delay minimization techniques are still missing in current logic synthesis technology. In [7], the RENO algorithm (which stands for REsynthesis for Network Optimization) was proposed for minimizing the area of multi-level combinational networks, and its effectiveness in designing minimal-area networks has been demonstrated. In this paper, we present improvements and extensions of the RENO algorithm for network delay minimization by using Boolean resynthesis techniques. We will discuss new algorithms for gate resynthesis which have not only reduced the processing time significantly, but also have improved the quality of minimization. Due to the generality of the gate resynthesis algorithms, we can minimize both delay and area of a network concurrently in a unified way, and network delay is reduced significantly with no or very small area penalty. Extensive experimental results and comparison with the speed_up algorithm in SIS-1.0 are presented.

Test pattern generation is getting much harder as the circuit size becomes larger. One problem is that it tends to take much time and another one is that it is difficult to detect redundant faults. Aiming to cope with these problem, an enhanced unique sensitization technique is proposed in this paper. This powerful global implication reduces the number of backtracks with reasonable computational time. And a fast test pattern generator featuring this unique sensitization demonstrates its performance using large benchmark circuits with over ten thousands of gates. It takes only a minute to detect all testable faults and to identify all redundant faults of 20,000 gates circuit on a workstation.

In this paper, a new method of synthesizing multi-level logic circuits directly from binary decision diagrams (BDDs) is proposed. In the simple multiplexer implementation, the depth of the synthesized circuit was always O (n), where n is the number of input variables. The new synthesis method attempts to reduce the depth of circuits. The depth of the synthesized circuits is O (log n log w) where w is the maximum width of given BDDs. The synthesized circuits are 2-rail-input 2-rail-output logic circuits. The circuits have good testability; it is proved that the circuits are robustly path-delay fault testable and also totally self-checking for single stuck-at faults.

We introduce automatic procedures for generating and verifying sufficient correctness properties of synchronous processors. The targeted circuits are synchronous array processors designed from localized, highly regular data dependency graphs (DDGs). The specification, in the form of a DDG, is viewed as a maximally parallel circuit. The implementation, on the other hand, is a (partially) serialized circuit. Since these circuits are not equivalent from an automata-theoretic viewpoint, we define the correctness of the implementation against the specification to mean that a certain relation (called the β-relation) holds between the two. We use a compositional approach to decouple the verification of the control circuitry from that of the data path, thereby gaining efficiency. An array processor in isolation may not have a definite flow of control, because control may reside in the data stream. Therefore, for the purpose of verification, we construct an auxiliary machine, which keeps a timing reference and generates control signals abstracted from a typical data stream. Sufficient correctness conditions are expressed as past-tense computation tree logic (CTL) formulae and verified by CTL model-checking procedures. Experimental results of the verification of a matrix multiplication array and a Gaussian elimination array are presented.

An attempt to apply neural networks to the acoustic diagnosis for the reciprocating compressor is described. The proposed neural network, Hybrid Neural Network (HNN), is composed of two multi-layered neural networks, an Acoustic Feature Extraction Network (AFEN) and a Fault Discrimination Network (FDN). The AFEN has multi-layers and the number of units in the middle hidden layer is smaller than the others. The input patterns of the AFEN are the logarithmic power spectra. In the AFEN, the error back propagation method is applied as the learning algorithm and the target patterns for the output layer are the same as the input patterns. After the learning, the hidden layer acquires the compressed input information. The architecture of the AFEN appropriate for the acoustic diagnosis is examined. This includes the determination of the form of the activation function in the output layer, the number of hidden layers and the numbers of units in the hidden layers. The FDN is composed of three layers and the learning algorithm is the same as the AFEN. The appropriate number of units in the hidden layer of the FDN is examined. The input patterns of the FDN are fed from the output of the hidden layer in the learned AFEN. The task of the HNN is to discriminate the types of faults in the compressor's two elements, the valve plate and the valve spring. The performance of the FDN are compared between the different inputs; the output of the hidden layer in the AFEN, the conventional cepstral coefficients and the filterbank's outputs. Furthermore, the FDN itself is compared to the conventional pattern recognition technique based on the feature vector distance, the Euclid distance measure, where the input is taken from the AFEN. The obtained results show that the discrimination accuracy with the HNN is better than that with the other combination of the discrimination method and its input. The output criteria of network for practical use is also discussed. The discrimination accuracy with this criteria is 85.4% and there is no case which mistakes the fault condition for the normal condition. These results suggest that the proposed decision network is effective for the acoustic diagnosis.

An algorithm interpolating parallel cross-sections between CT slices is described. Contours of equiscalar or constant-density surfaces on cross-sections are directly obtained as non-intersecting loops from grayscale slice images. This algorithm is based on a general algorithm that the authors have proposed earlier, constructing triangulated orientable closed surfaces from grayscale volumes and is particularly suited for a new technique, called laser stereolithography, which creates real 3D plastic objects using UV laser to scan and harden liquid polymer. The process of laser stereolithography is executed slice by slice, and this technique really requires some interpolation of intermediate cross-sections between slices. For visualizing, surfaces are only expected to be shaded almost continuously. The local defects are invisible and not cared about if the picture resolution is rather poor. On the contrary, topological faults are fatal to construct solid models by laser stereolithography, i.e., every contour line on cross-sections must be closed with no intersection. Not a single break of a contour line is tolerated. We already have many algorithms available for equiscalar surface construction, and it seems that if we cut the surfaces, then contour lines could be obtained. However, few of them are directly applicable to solid modeling. Marching cubes algorithm, for example, does not ensure the consistency of surface topology. Our algorithm guarantee an adequate topology of contour lines.

This paper introduces the concept of an extended pseudo-biorthogonal basis" (EPBOB), which is a generalization of the concepts of an orthonormal (OB), a biorthonormal (BOB), a pseudo-orthogonal (POB), and a pseudo-biorthogonal (PBOB) bases. Let HN be a subspace of a Hilbert space H. The concept of EPBOB says that we can always construct a set of 2M (MN) elements of H but not necessarily all in HN such that like BOB any element f in HN can be expressed by fMΣm=1(f,φ*m)φm. For a better understanding and a wide application of EPBOB, this paper provides their characterization and shows how they preserve the formalism of BOB. It also shows how to construct them.

A new trial of statistical evaluation for an output response of power linear type acoustic systems with nonstationary random input is proposed. The purpose of this study is to predict the output probability distribution function on the basis of a standard type pre-experiment in a laboratoty. The statistical properties like nonstationarity, non-Gamma distribution property and various type linear and non-linear correlations of input signal are reflected in the form of differential operation with respect to distribution parameters. More concretely, the pre-experiment is carried out for a power linear acoustic system excited only by the Gamma distribution type sandard random input. Considering the non-negative random property for the output response of a power linear system, the well-known statistical Laguerre expansion series type probability expression is first employed as the framework of basic probability distribution expression on the output power fluctuation. Then, the objective output probability distribution for a non-stationary case can be easily derived only by successively employing newly introduced differential operators to this basic probability distribution of statistical Laguerre expansion series type. As an application to the actual noise environment, the proposed method is employed for an evaluation problem on the stochastic response probability distribution for an acoustic sound insulation system excited by a nonstationary input noise.

Recently, a family of 4-phase sequences (alphabet {1,j,-1,-j}) was discovered having the same size 2r+1 and period 2r-1 as the family of binary (i.e., {+1, -1}) Gold sequences, but whose maximum nontrivial correlation is smaller by a factor of 2. In addition, the worst-case correlation magnitude remains the same for r odd or even, unlike in the case of Gold sequences. The family is asymptotically optimal with respect to the Welch lower bound on Cmax for complex-valued sequences and the sequences within the family are easily generated using shift registers. This paper aims to provide a more accessible description of these sequences.

In multidimensional signal sampling, the orthogonal sampling scheme is the simplest one and is employed in various applications, while a non-orthogonal sampling scheme is its alternative candidate. The latter sampling scheme is used mainly in application where the reduction of the sampling rate is important. In three-dimensional (3-D) signal processing, there are two typical sampling schemes which belong to the non-orthogonal samplings; one is face-centered cubic sampling (FCCS) and the other is body-centered cubic sampling (BCCS). This paper proposes a new design method for 3-D band-limiting FIR filters required for such non-orthogonal sampling schemes. The proposed method employs the McClellan transformation technique. Unlike the usual 3-D McClellan transformation, however, the proposed design method uses 2-D prototype filters and 2-D transformation filters to obtain 3-D FIR filters. First, 3-D general sampling theory is discussed and the two types of typical non-orthogonal sampling schemes, FCCS and BCCS, are explained. Then, the proposed design method of 3-D bandlimiting filters for these sampling schemes is explained and an effective implementation of the designed filters is discussed briefly. Finally, design examples are given and the proposed method is compared with other method to show the effectiveness of our methos.

The well known optimum approach to detect spread spectrum signals transmitted in bursts over frequency selective radio channels is matched filtering, which performs despreading, and subsequent Viterbi equalization (VE) to cope with intersymbol interference (ISI). With respect to complexity, VE is feasible only if data modulation schemes with a few symbol levels as e.g. 2PSK are used and if the delay spread of the channel is not too large. The paper gives a survey of suboptimum data detectors based on linear block estimation. Such data detectors are less expensive than VE especially in the case of multilevel data modulation schemes as 4PSK or 16QAM. Special emphasis is laid on data detectors based on Gauss-Markoff estimation because these detectors combine the advantages of unbiasedness and minimum variance of the estimate. In computer simulations, the Gauss-Markoff estimation algorithm is applied to spread spectrum burst transmission over radio channels specified by COST 207. It is shown that the SNR degradation which is a measure of the suboptimality of the detector does not exceed a few dB, and that even moderate spectrum spreading considerably reduces the detrimental effect of channel frequency selectivity.

We have fabricated bi-epitaxial grain boundary junctions in YBa2Cu3O7δ (YBCO) thin films by using SrTiO3 (STO) seed layers on MgO(100) substrate. YBCO film growing over the STO seed layer has a different in-plane orientation from YBCO film without the seed layer, so artificial grain boundaries were created at the edge of the seed layer. The fabricated junctions have high Tc (up to 80 K), and constant-voltage current steps are observed in response to 12.1 GHz microwave radiation. Moreover, some of the junctions show characteristic current-voltage curves comprising not only an usual Josephson-like characteristic but also a low critical current due to the flux creep. This suggests that the two characteristic parts are likely to be connected in series at the junction region.