This paper presents a new distributed scheduling architecture for wireless ATM networks. Usually, in WATM scheduling architectures, a fixed order is defined among the different connections through their ATM service category (CBR VBR ABR UBR). We argue that although this static priority is easier to implement, this type of precedence is not necessarily a good choice for the MAC layer. The MAC layer scheduling should define an order such that it uses efficiently the resources while providing quality of service (QoS) guarantees. In this spirit, our architecture delays (without violating their QoS) the real time connections in order to improve the performance of non real time connections.

Low voltage (LV) analog circuit design techniques are addressed in this tutorial. In particular, (i) technology considerations; (ii) transistor model capable to provide performance and power tradeoffs; (iii) low voltage implementation techniques capable to reduce the power supply requirements, such as bulk-driven, floating-gate, and self-cascode MOSFETs; (iv) basic LV building blocks; (v) multi-stage frequency compensation topologies; and (vi) fully-differential and fully-balanced systems.

Input buffered switches most efficiently use memory and switch bandwidth. With Virtual Output Queueing (VOQ), head-of-line blocking can be avoided, thus breaking the throughput barrier of 58.6%. In this paper a switch architecture based on VOQ is proposed, which offers deterministic and stochastic delay bounds for prioritized traffic. This is achieved by a hybrid static and dynamic arbitration scheme, which matches ports both by a precalculated schedule and realtime calculations. By using weighted dynamic arbitration algorithms 100% throughput with lowest delays under all admissible traffic can be achieved. An integrated global priority scheme allows the multiplexing of realtime and data traffic. Following the arbitration decision, a cell scheduler decides locally in the input ports upon the next connection from which a cell is forwarded. Cell scheduling based on earliest-deadline-first (EDF) is shown to perform similar to its behaviour in an output-queued switch.

We propose a new sampling method for 2D and 3D implicit surfaces. The method is based on a stochastic process defined by the Langevin equation with a Gaussian random-force term. Our Langevin equation describes a stochastic-dynamical particle, which develops in time confined around the sampled implicit surface with small width. Its numerically generated solutions can be easily moved onto the surface strictly with very few iteration of the Newton correction. The method is robust in a sense that an arbitrary number of sample points can be obtained starting from one simple initial condition. It is because (1) the time development of the stochastic-dynamical particle does not terminate even when it reaches the sampled implicit surface, and (2) there is non-zero transition probability from one disconnected component to another. The method works very well for implicit surfaces which are complicated topologically, mathematically, and/or in shape. It also has some advantageous features in rendering 3D implicit surfaces. Many examples of applying our sampling method to real 2D and 3D implicit surfaces are presented.

Future high-speed switches and routers will be expected to support a large number of ports at high line rates carrying traffic with diverse statistical properties. Accordingly, scheduling mechanisms will be required to handle Tbit/sec aggregated capacity while providing quality of service (QoS) guarantees. In this paper a novel high-capacity switching scheme for ATM/WDM networks is presented. The proposed architecture is contention-free, scalable, easy to implement and requires no internal "speedup. " Non-uniform destination distribution and bursty cell arrivals are examined when studying the switching performance. Simulation results show that at an aggregated throughput of 1 Tbit/sec, low latency is achieved, yielding a powerful solution for high-performance packet-switch networks.

We introduce a new wavelet image coding framework using context-based zerotree quantization, where an unique and efficient method for optimization of zerotree quantization is proposed. Because of the localization properties of wavelets, when a wavelet coefficient is to be quantized, the best quantizer is expected to be designed to match the statistics of the wavelet coefficients in its neighborhood, that is, the quantizer should be adaptive both in space and frequency domain. Previous image coders tended to design quantizers in a band or a class level, which limited their performances as it is difficult for the localization properties of wavelets to be exploited. Contrasting with previous coders, we propose to trace the localization properties with the combination of the tree-structured wavelet representations and adaptive models which are spatial-varying according to the local statistics. In the paper, we describe the proposed coding algorithm, where the spatial-varying models are estimated from the quantized causal neighborhoods and the zerotree pruning is based on the Lagrangian cost that can be evaluated from the statistics nearby the tree. In this way, optimization of zerotree quantization is no longer a joint optimization problem as in SFQ. Simulation results demonstrate that the coding performance is competitive, and sometimes is superior to the best results of zerotree-based coding reported in SFQ.

This paper proposes an Iterated Function System (IFS) which can reduce effects of quantization errors of the IFS parameters. The proposed method skips conventional analog-parameter search and directly selects optimum IFS parameters from pools of discrete IFS parameters. In conventional IFS-based image coding the IFS parameters are quantized after their analog optimum values are determined. The image reconstructed from the quantized parameters is degraded with errors that are traced back to quantization errors amplified in the iterated mappings. The effectiveness of this new realistic approach is demonstrated by simulation results over the conventional method.

The mathematical theory of bicomplex electromagnetic waves in two-dimensional scattering and diffraction problems is developed. The Vekua's integral expression for the two-dimensional fields valid only in the closed source-free region is generalized into the radiating field. The boundary-value problems for scattering and diffraction are formulated in the bicomplex space. The complex function of a single variable, which obeys the Cauchy-Riemann relations and thus expresses low-frequency aspects of the near field at a wedge of the scatterer, is connected with the radiating field by an integral operator having a suitable kernel. The behaviors of this complex function in the whole space are discussed together with those of the far-zone field or the amplitude of angular spectrum. The Hilbert's factorization scheme is used to find out a linear transformation from the far-zone field to the bicomplex-valued function of a single variable. This transformation is shown to be unique. The new integral expression for the field scattered by a thin metallic strip is also obtained.

Combined input output queued (CIOQ) architecture such as crossbar with speedup has recently been proposed to build a large capacity switch for broadband integrated services networks. It was shown that, for a speedup factor of 2, a CIOQ switch can achieve 100% throughput with a simple maximal matching algorithm. Achieving 100% throughput, however, is not sufficient for per-connection quality of service (QoS) guarantee. In [2],[3], it is proved that a CIOQ switch with a speedup factor of 2 can exactly emulate an output queued (OQ) switch if stable matching is adopted. Unfortunately, the complexity of currently known algorithms makes stable matching impractical for high-speed switches. In this paper, we propose a new matching algorithm called the least cushion first/most urgent first (LCF/MUF) algorithm and formally prove that a CIOQ switch with a speedup factor of 2 can exactly emulate an OQ switch which adopts any service discipline for cell transmission. A potential implementation of our proposed matching algorithm for strict priority service discipline is also presented.

A quantization-based watermarking system for motion pictures is proposed. In particular, methods for improving the image quality of watermarked video, the watermarking data tolerance, and the accuracy of watermark data detection are described. A quantitative evaluation of the reliability of watermarked data, which has not generally been discussed up to now, is also performed.

Measurement of the viscosity of liquid using a piezoelectric disk is described. Experiments with a radial expansion mode of a piezoceramic disk were carried out for water-glycerin mixture samples. Resonant resistance has linearity to the square root of the product of density and viscosity of a liquid around 113 kHz.

We report on the fabrication and operation of all-NbN single flux quantum (SFQ) circuits with resistively shunted NbN/AlN/NbN tunnel junctions fabricated on silicon substrates. The critical current varied by about 5% in 400 NbN/AlN/NbN junction arrays, where the junction area was 88 µm2. Critical current densities of the NbN/AlN/NbN tunnel junctions showed exponential dependence on the deposition time of the AlN barrier. By using the 12-nm-thick Cu film as shunted resistors, non-hysteretic current-voltage characteristics were achieved. From dc-SQUID measurements, the sheet inductance of our NbN stripline was estimated to be around 1.2 pH at 4.2 K. We designed and fabricated circuits consisting of dc/SFQ converters, Josephson transmission lines, and T flip-flop-based SFQ/dc converters. The circuits demonstrated correct operation with a bias margin of more than 15% at 4.2 K.

A portable cryo-system using a high-Tc SQUID for the measurement of the remanant magnetic field of a rock specimen was designed and fabricated. The sensing surface of the SQUID faces upward in our system, although the system for bio-magnetics faces down. The SQUID is cooled by liquid nitrogen via a sapphire heat transfer rod. The total heat transfer of the system was measured by means of a boiling-off method and was found to be 1.65 W. It was demonstrated that the system can be operated for more than 17 hours without any maintenance such as filling with liquid nitrogen. The system was applied to the measurement of the remanent magnetic field distributions of rock samples cored from deep underground. We have successfully measured the distributions.

Methods to discover laws are reviewed from among both statistical approach and artificial intelligence approach with more emphasis placed on the latter. Dimensions discussed are variable dependency checking, passive or active data gathering, single or multiple laws discovery, static (equilibrium) or dynamic (transient) behavior, quantitative (numeric) or qualitative or structural law discovery, and use of domain-general knowledge. Some of the representative discovery systems are also briefly discussed in conjunction with the methods used in the above dimensions.

We report on progress in the development of high current density NbN/AlN/NbN tunnel junctions for application as submillimeter wave SIS mixers. A ultra-high current density up to 120 kA/cm2, roughly two orders of magnitude larger than any reported results for all-NbN tunnel junctions, was achieved in the junctions. The magnetic field dependence and temperature dependence of critical supercurrents were measured to investigate the Josephson tunneling behaviour of critical supercurrents in the high-Jc junctions. We have developed a low-noise quasi-optical SIS mixer with the high-current density NbN/AlN/NbN junctions and two-junction tuning circuits which employ Al/SiO/NbN microstriplines. The tuning characteristics of the mixer were investigated by measuring the response in the direct detection mode by using the Fourier Transform Spectrometer (FTS) and measuring the response in the heterodyne detection mode with the standard Y-factor method at frequencies from 670 to 1082 GHz. An uncorrected double sideband receiver noise temperature of 457 K (12hν/kB) was obtained at 783 GHz.

Recent progress of high-temperature superconductor Josephson junction technology is reviewed in the light of the future application to digital circuits. Among various types of Josephson junctions so far developed, ramp-edge-type junctions with a barrier layer composed of oxide materials in the vicinity of metal-insulator transition seem to offer a unique opportunity to fulfill all the requirements for digital circuit applications by virtue of their small junction dimensions, overdamped properties and relatively high IcRn product values at the temperature of around 30-40 K. Recently developed interface engineered junctions can be classified as junctions of this type. These junctions also raise an interesting problem in physics concerning the possibility of resonant tunneling of Cooper pairs via localized states in the barrier. From the viewpoint of practical applications, the improvement of the spread of the junction parameters is still a serious challenge to the present fabrication technology. Although interface engineered junctions seem to be most promising in this regard at present, 1σ spread of around 8% in the present fabrication technology is far from satisfactory for the fabrication of large-scale integrated circuits. The detailed understanding of the barrier formation mechanism in the interface engineered junction is indispensable not only for advancing this particular fabrication technology but also for improving other junction technology utilizing ramp-edge structures.

It is the purpose of this paper to review the generation of quantized voltage steps in Josephson-junctions, and also the recent practical application of these precise measurements. A 10-V Josephson-junction-array-voltage standard system has been established with a Josephson-junction-array, a phase-locked millimeter wave, and a precise null-detection system. Based on these technologies, the AC Josephson effect has been applied to other precise measurements such as DC error voltage of a multi-integrating analog-to-digital converter and for a pulse-width-modulation type precise voltage calibrator.

Recent progresses in high Tc superconducting quantum interference device (SQUID) magnetometers are discussed. First, intrinsic sensitivity of the SQUID at T=77 K is discussed. For this purpose, transport and noise properties of the bicrystal junction are clarified, and optimization of junction parameters is shown. We also discuss the quality of the SQUID from a comprehensive comparison between experiment and simulation of the SQUID characteristics. Next, we discuss issues to guarantee correct operation of the SQUID magnetometer in noisy environment, such as a method to avoid flux trapping due to earth magnetic field, high-bandwidth electronics and gradiometer. Finally, we briefly describe application fields of the high Tc magnetometer.

We have developed a parameter optimization tool, Monte Carlo Josephson simulator (MJSIM), for rapid single flux quantum (RSFQ) digital circuits based on a Monte Carlo yield analysis. MJSIM can generate a number of net lists for the JSIM, where all parameter values are varied randomly according to the Gaussian distribution function, and calculate the circuit yields automatically. MJSIM can also produce an improved parameter set using the algorithm of the center-of-gravity method. In this algorithm, an improved parameter vector is derived by calculating the average of parameter vectors inside and outside the operating region. As a case study, we have optimized the circuit parameters of an RS flip-flop, and investigated the validity and efficiency of this optimization method by considering the convergency and initial condition dependence of the final results. We also proposed a method for accelerating the optimization speed by increasing 3σ spreads of the parameter distribution during the optimization.

We propose a universal NAND logic gate based on single flux quantum (SFQ) logic. The NAND gate enables the construction of any logic circuits. In the proposed gate, three superconducting loops share two Josephson junctions (JJs). The critical currents of the JJs were designed to allow each of any two loops to trap an SFQ at the same time. We simulated dynamic operation of this NAND gate. The results show that the NAND gate can operate with a delay time of 45 ps, and the power consumption of this circuit is close to 0.06 µW/gate.