The instruction set architecture of MBP-light, a dedicated processor for the DSM (Distributed Shared Memory) management of JUMP-1 is analyzed with a real prototype. The Buffer-Register Architecture proposed for MBP-core improves performance with 5.64% in the home cluster and 6.27% in a remote cluster. Only a special instruction for hashing cluster address is efficient and improves the performance with 2.80%, but other special instructions are almost useless. It appears that the dominant operations in the DSM management program were handling packet queues assigned into the local cluster. Thus, common RISC instructions, especially load/store instructions, are frequently used. Separating instruction and data memory improves performance with 33%. The results suggest that another alternative which provides separate on-chip cache and instructions dedicated for packet queue management is advantageous.

High-temperature stability of copper (Cu) gate AlGaN/GaN high electron mobility transistors (HEMTs) was investigated. Samples were annealed at various temperatures to monitor the changes on device performances. Current-voltage performance such as drain-source current, transconductance, threshold voltage and gate leakage current has no obvious degradation up to annealing temperature of 500 and time of 5 minutes. Also up to this temperature, no copper diffusion was found at the Cu and AlGaN interface by secondary ion mass spectrometry determination. At annealing temperature of 700 and time of 5 minutes, device performance was found to have degraded. Gate voltage swing increased and threshold voltage shifted due to Cu diffusion into AlGaN. These results indicate that the Schottky contact and device performance of Cu-gate AlGaN/GaN HEMT is stable up to annealing temperature of 500. Cu is a promising candidate as gate metallization for high-performance power AlGaN/GaN HEMTs.

Given the importance of the traffic on modern communication networks, advanced error correction methods are needed to overcome the changes expected in channel quality. Conventional countermeasures that use high dimensionality parity codes often fail to provide sufficient error correction capability. We propose a parity code with high dimensionality that is iteratively decoded. It provides better error correcting capability than conventional decoding methods. The proposal uses the steepest descent method to increase code bit reliability and the coherency between parities and code bits gradually. Furthermore, the quantization of the decoding algorithm is discussed. It is found that decoding with quantization can keep the error correcting capability high.

We describe 150-nm-thick collector InP-based double heterojunction bipolar transistors with two types of thin pseudomorphic bases. The emitter and collector layers are designed for high collector current operation. The collector current blocking is suppressed by the compositionally step-graded collector structure even at JC of over 500 kA/cm2 with practical breakdown characteristics. An HBT with a 20-nm-thick base achieves a high fT of 351 GHz at high JC of 667 kA/cm2, and a 30-nm-base HBT achieves a high value of 329 GHz for both fT and fmax at JC of 583 kA/cm2. An equivalent circuit analysis suggests that the extremely small carrier-transit-delay contributes to the ultrahigh fT.

In this paper, we investigate Tanner's lower bound for the minimum distance of regular LDPC codes based on combinatorial designs. We first determine Tanner's lower bound for LDPC codes which are defined by modifying bipartite graphs obtained from combinatorial designs known as Steiner systems. Then we show that Tanner's lower bound agrees with or exceeds conventional lower bounds including the BCH bound, and gives the true minimum distance for some EG-LDPC codes.

RHiNET-3/SW is the third-generation switch used in the RHiNET-3 system. It provides both low-latency processing and flexible connection due to its use of a credit-based flow-control mechanism, topology-free routing, and deadlock-free routing. The aggregate throughput of RHiNET-3/SW is 80 Gbps, and the latency is 140 ns. RHiNET-3/SW also provides a hop-by-hop retransmission mechanism. Simulation demonstrated that the effective throughput at a node in a 64-node torus RHiNET-3 system is equivalent to the effective throughput of a 64-bit 33-MHz PCI bus and that the performance of RHiNET-3/SW almost equals or exceeds the best performance of RHiNET-2/SW, the second-generation switch. Although credit-based flow control requires 26% more gates than rate-based flow control to manage the virtual channels (VCs), it requires less VC memory than rate-based flow control. Moreover, its use in a network system reduces latency and increases the maximum throughput compared to rate-based flow control.

We propose and describe a free-space optical interconnection device with a photorefractive semi-linear resonator. The hologram in the photorefractive crystal is, in general, volatile and the erasing of it coincides with the diffraction of the signal beam. Therefore we have to reform the hologram again after several transmissions of the data or use some fixing techniques such as thermal fixing and electrical fixing. In our interconnection device, the hologram is enhanced by the feedback beam that is a part of the input signal divided by the beam splitter within semi-linear resonator, therefore the sustentation time of the connection can be extended. We explain the sustentation mechanism and investigate the optimum reflectivity of the beam splitters, which determine the feedback rate of the input signal, within feedback circuit for the high output conversion efficiency. We also analyze the coupling strength threshold for sustentation of the connection. We give a basic experiment on 33 interconnection by using BaTiO3 crystal and Ar+ laser whose wavelength is 514 [nm]. We show that the connections are held for long time without the continuous illumination of the control beam.

We propose an analysis method for Franz-Keldysh (FK) oscillations appearing in photoreflectance (PR) spectra of heterojunction device structures, which enables precise and simultaneous evaluation of the built-in electric field strength and band-gap energy. Samples for PR measurements were n+-GaAs/n-Al0.3 Ga0.7 As/i-GaAs heterostructures with different Al0.3Ga0.7As-layer thickness. We have found that the phase of the FK oscillations originating from the i-GaAs buffer layer depends on the Al0.3 Ga0.7 As-layer thickness. We have derived a calculation model for FK oscillations that includes the interference of probe light. From the comparison of the calculated spectra with the measured spectra, we conclude that mixing of the real and imaginary parts of a modulated dielectric function, which is caused by the probe-light interference, gives rise to the phase shift of the FK oscillations. Our FK-oscillation analysis method reduces ambiguity in the estimation of band-gap energy that is considerable in a conventional analysis.

This paper describes a method for the fast evaluation of the Sommerfeld integrals for modeling a vertical dipole antenna array in a borehole. When we analyze the antenna inside a medium modeled by multiple cylindrical layers with the Method of Moment (MoM), we need a Green's function including the scattered field from the cylindrical boundaries. We focus on the calculation of Green's functions under the condition that both the detector and the source are situated in the innermost layer, since the Green's functions are used to form the impedance matrix of the antenna. Considering bounds on the location of singularities on a complex wave number plane, a fast convergent integration path where pole tracking is unnecessary is considered for numerical integration. Furthermore, as an approximation of the Sommerfeld integral, we describe an asymptotic expansion of the integrals along the branch cuts. The pole contribution of TM01 and HE11 modes are considered in the asymptotic expansion. To obtain numerical results, we use a fast convergent integration path that always proves to be accurate and efficient. The asymptotic expansion works well under specific conditions. The Sommerfeld integral values calculated with the fast evaluation method is used to model the array antenna in a borehole with the MoM. We compare the MoM data with experimental data, and we show the validity of the fast evaluation method.

In this letter, a new output feedback tracking control using a fuzzy disturbance observer (FDO) is proposed and its application to control of a nonlinear system in the presence of the internal parameter perturbation and external disturbance is presented. An FDO using a filtered signal is developed and the high gain observer (HGO) is employed to implement the output feedback tracking control. It is shown in a rigorous manner that all the errors involved can be kept arbitrarily small. Finally, the effectiveness and the feasibility of the suggested method is demonstrated by computer simulation.

Broadcast disks are suited for disseminating information to a large number of clients in mobile computing environments. In broadcast disks, the server continuously and repeatedly broadcasts all data items in the database to clients without specific requests. The clients monitor the broadcast channel and read data items as they arrive on the broadcast channel. The broadcast channel then becomes a disk from which clients can read data items. In this paper, we propose a cache conscious concurrency control (C4) algorithm to preserve the consistency of read-only client transactions, when the values of broadcast data items are updated at the server. The C4 algorithm is novel in the sense that it can reduce the response time of client transactions with minimal control information to be broadcast from the server. This is achieved by the judicious caching strategy of the client and by adjusting the currency of data items read by the client.

In this paper, we propose the soft boundary concept achieved by dynamic tilted antenna to solve the issue of traffic congestion occurred in cellular wireless systems. The tilted antenna array can provide the merit of traffic balance and also achieve the optimization of the signal-to-interference ratio (SIR) at receivers by automatically tilting the antenna and implementing the soft boundary among cells, corresponding to the variation of traffic. According to our results, it is shown that power ratio control do not necessarily improved system performance when there is a large variation in traffic because it only control power levels. Also the properly chosen angle of tilt antenna can relieve the traffic congestion and perform the system performance optimization.

Field Configurable Self-assembly is a novel programmable force field based heterogeneous integration technology. Herein, we demonstrate application of the method to rapid, parallel assembly of similar and dissimilar sub-200 µm GaAs-based light emitting diodes at silicon chip substrates. We also show that the method is compatible with post-process collective wiring techniques for fully planar hybrid integration of active devices.

In this paper, a new Hierarchical Sum of Double Difference metric, HSDD, is introduced. It is shown, as opposed to conventional Sum of Absolute Difference (SAD) metric, how this zerotree coding aware metric can jointly constrain the motion vector searching for both temporal and spatial (quad-tree) directions under multiresolution motion estimation framework. The reward from the temporal-spatial co-optimization concept of HSDD is that fewer bits are spent later for describing the isolated zeros. The embedded wavelet video coder using HSDD metric was tested with a set of video sequences and the compression performance seems to be promising.

We have developed a novel self-alignment process using the surface tension of the liquid resin for assembly of electronic and optoelectronic devices. Due to their characteristics of low surface tension, however, the parametric design guidelines are necessary for resin self-alignment capability. In this paper, a shape prediction mathematical model and a numerical method are developed. The developed system is capable of achieving the liquid joint geometry and the parametric design for self-alignment capability. The influences of geometric parameters such as liquid volume, component weight, pad radius, liquid surface tension on the shape of liquid joint are investigated. Furthermore, the parametric design guidelines considered the process-related practical matters of misalignment level, distribution of the supplied liquid volumes and coplanarity deviation includes difference of the height between the pads are provided.

We study the advantages and limitations of InP/GaAsSb/InP DHBTs for high-speed digital circuit applications. We show that the high-current performance limitation in these devices is electrostatic in nature. Comparison of the location of collector current blocking in various collector designs suggests a smoother, more gradual onset of blocking effects in type-II collectors. A comparison of collector current blocking effects between InP/GaAsSb--based and various designs of InP/GaInAs--based DHBTs provides support for our analysis.

High-frequency characterization and delay-time analysis have been performed for a short channel AlGaN/GaN heterojunction FET. The fabricated device with a short gate length (Lg) of 0.07 µm exhibited an extrinsic current gain cutoff frequency of 81 GHz and a maximum frequency of oscillation of 190 GHz with a maximum stable gain (MSG) of 8.2 dB at 60 GHz. A new scheme for the delay-time analysis was proposed, in which the effects of rather large series resistance RS + RD are properly taken into account. By applying the new scheme to a device with Lg=0.25 µm, we obtained an effective high-field electron velocity of 1.75107 cm/s, which is consistent with our previous results calculated using Monte Carlo simulation.

We present ultra low noise- and wide dynamic range performances of an AlGaN/GaN heterostructure FET (HFET). An HFET fabricated on a high quality epitaxial layers grown on a semi-insulating SiC substrate exhibited impressively low minimum noise figure (NF min ) of 0.4 dB with 16 dB associated gain at 2 GHz. The low NF (near NF min ) operation was possible in a wide drain bias voltage range, i.e. from 3 V to 15 V. At the same time, the device showed low distortion character as indicated by the high third order input intercept point (IIP3), +13 dBm. The excellent characteristics are attributed to three major factors: (1) high quality epitaxial layers that realized a high transconductance and very low buffer leakage current; (2) excellent device isolation made by selective thermal oxidation; (3) ultra low gate leakage current realized by Pd based gate. The results demonstrate that the AlGaN/GaN HFET is a strong candidate for front-end LNAs in various mobile communication systems where both the low noise and the wide dynamic range are required.

A high-speed high-resolution sample-and-hold amplifier (SHA) is designed for time-interleaved analog-to-digital converter applications. Using the techniques of precharging and output capacitor coupling can mitigate the stringent performance requirements for the opamp, resulting in low power dissipation. Implemented in a standard 0.25 µm CMOS technology, the SHA achieves 80 dB spurious-free dynamic range (SFDR) for a 1.8 Vpp output at 100 MHz Nyquist sampling rate. The SHA occupies a die area of 0.35 mm2 and dissipates 33 mW from a single 2.5 V supply.

In order to clarify the mechanism of gate leakage in AlGaN/GaN heterostructure field effect transistors (HFETs), temperature (T)-dependent current-voltage (I-V) characteristics of Ni/n-AlGaN Schottky contact were measured in detail. Large deviations from the thermionic emission transport were observed in I-V-T behavior with anomalously large reverse leakage currents. An analysis based on the thin surface barrier (TSB) model showed that the nitrogen-vacancy-related near-surface donors play a dominant role in the leakage through the AlGaN Schottky interface. As a practical scheme for suppressing the leakage currents, use of an insulated gate (IG) structure was investigated. As the insulator, Al2O3 was selected, and an Al2O3 IG structure was formed on the AlGaN/GaN heterostructure surface after an ECR-N2 plasma treatment. An in-situ XPS analysis exhibited successful formation of an ultrathin stoichiometric Al2O3 layer which has a large conduction band offset of 2.1 eV at the Al2O3/Al0.3Ga0.7N interface. The fabricated Al2O3 IG HFET achieved pronounced reduction of gate leakage, resulting in the good gate control of drain currents up to VGS = +3 V. The maximum drain saturation current and transconductance were 0.8 A/mm and 120 mS/mm, respectively. No current collapse was observed in the Al2O3 IG-HFETs, indicating a remarkable advantage of the present Al2O3-based insulated gate and passivation structure.