This paper reports the implementation in three dimensions (3D) of diffusion models for low dose implanted dopants in silicon and the various numerical issues associated with it. In order to allow the end-users to choose between high accuracy or small calculation time, a conventional and 5-species diffusion models have been implemented in the 3D module DIFOX-3D belonging to the PROMPT plateform. By comparison with one and two-dimensional (1D and 2D) simulations performed with IMPACT-4, where calibrated models exist, the validity of this 3D models have been checked. Finally, the results obtained for a 3-dimensional simulation of a rapid thermal annealing step involved in the manufacturing of a MOS transistor are presented what show the capability of this module to handle the optimization of real devices.

This paper newly proposes radio-over-fiber systems using cascaded radio-to-optic direct conversion (ROC) scheme. The ROC system can convert a radio signal into an optical signal with the same signal format. The received carrier-to-noise ratio (CNR) performance of the radio-over-fiber systems using the ROC/heterodyne detection (HD) scheme and the ROC/self-heterodyne detection (SHD) scheme are theoretically analyzed. The optimization of an optical modulation index (OMI) in each radio base station (RBS) is also presented. By using the proposed OMI optimization method, the ROC/HD and the ROC/SHD schemes are shown to provide approximately 16 dB and 14 dB improvement over the intensity modulation/direct detection scheme when the number of RBS is 20 and the radio-frequency (RF) signal bandwidth is 150 MHz, respectively. The ROC/SHD scheme enables a receiver structure to become simple while still achieving high received CNR.

In this paper the novel method of "weighted OFDM" is addressed. Different types of weighting factors (including Rectangular, Bartlett, Gaussian, Raised cosine, Half-sin and Shanon) are considered. The impact of weighting of OFDM on the peak-to-average power ratio (PAPR) is investigated by means of simulation and is compared for the above mentioned weighting factors. Results show that by weighting of the OFDM signal the PAPR reduces. Bit error performance of weighted multicarrier transmission over a multipath channel is also investigated. Results indicate that there is a trade off between PAPR reduction and bit error performance degradation by weighting.

A Schottky contact model was implemented as a boundary condition for Monte Carlo device simulations. Unlike the ideal ohmic contact, the thermal equilibrium is unnecessary around the Schottky contact. Therefore, the wide region with high impurity concentration around the contact is not required to maintain the thermal equilibrium, which means that it is possible to avoid assigning a lot of particles to the low-field region. The validity of the present boundary condition for contacts was verified by simulating a rectifying characteristic of a Schottky barrier diode. As an application example using the present contact model, we simulated transport in n+nn+ structures with sub-0.1 µm channel lengths. We observed direction dependence of the electron velocity dispersion, which indicates that the direction dependence of the diffusion constant or the carrier temperature should be taken into account in the hydrodynamic simulation for sub-0.1 µm devices.

In this article, an efficient vector quantization (VQ) scheme called side-match finite-state vector quantization with adaptive block classification is presented for image compression. It makes use of edge information contained in image in additional to the average values of blocks forming the image. In order to achieve low bit rate coding while preserving good quality images, neighboring blocks are utilized to predict the class of current block. Image blocks are mainly classified as edge blocks and non-edge blocks in this coding scheme. To improve the coding efficiency, edge blocks and non-edge blocks are further reclassified into different classes, respectively. Moreover, the number of bits for encoding an image is greatly reduced by foretelling the class of input block and applying small state codebook in corresponding class. The improvement of the proposed coding scheme is attractive as compared with other VQ techniques.

This paper experimentally demonstrates the possibility of 2-Mbps data transmission using a 5-MHz bandwidth (chip rate of 4.096 Mcps) wideband DS-CDMA (W-CDMA) mobile radio link in frequency-selective multipath fading environments. To reduce the mobile station transceiver complexity, three-orthogonal code multiplexing with the spreading factor (SF) of 4 is employed. In such a small SF transmission, the increased multipath interference (MPI) significantly degrades the transmission performance. We consider two-branch antenna diversity reception and fast transmit power control (TPC) as well as channel coding to mitigate the influence of MPI. Laboratory experimental results show that the use of antenna diversity reception is significant and that the fast TPC improves the transmission performance. Furthermore, the impact of the fading maximum Doppler frequency, fD, and that of the channel coding interleaving size, Tint, on the achievable BER performance are also investigated.

We examine the detection of coded hybrid direct-sequence frequency-hopped spread-spectrum signals in the presence of narrowband interference. Since blind interference suppression requires a reliable estimate of the data, while at the same time data decoding requires interference suppression, we advocate an iterative ("turbo") detection scheme whereby information is exchanged between the interference suppressor and the soft-input soft-output decoder. Several suppression schemes are examined and compared. Simulation results show that this new scheme is robust, i.e., exhibits good performance under a modicum of assumptions on the interference structure. Turbo codes and convolutional codes are compared, showing that the former perform better.

Credit-based electronic payment systems are considered to play important roles in future automated payment systems. Like most other types of payment systems, however, credit-based systems proposed so far generally involve computationally expensive cryptographic operations. Such a relatively heavy computational load is preventing credit-based systems from being used in applications which require very fast processing. A typical example is admission-fee payment at the toll gate of an expressway without stopping a vehicle that travels at a high speed. In this article, we propose a very fast credit-based electronic payment protocol for admission-fee payment. More specifically, we propose a payment system between a high-speed vehicle and a toll gate which uses only very simple and fast computations. The proposed system makes use of an optimized Key Pre-distribution System (or KPS) to obtain high resistance against collusion attacks.

An MPEG-2 422P@HL encoder chip set composed of a preprocessing LSI, an encoding LSI, and a motion estimation LSI is described. This chip set realizes a two-type scalability of picture resolution and quality, and executes a hierarchical coding control in the overall encoder system. Due to its scalable architecture, the chip set realizes a 422P@HL video encoder with multi-chip configuration. This single encoding LSI achieves 422P@ML video, audio, and system encoding in real time. It employs an advanced hybrid architecture with a 162 MHz media processor and dedicated video processing hardware. It also has dual communication ports for parallel processing with multi-chip configuration. Transferring of reconstructed data and macroblock characteristic data between neighboring encoder modules is executed via these ports. The preprocessing LSI is fabricated using 0.25 micron three-layer metal CMOS technology and integrates 560 K gates in an area of 12.0 mm 12.0 mm . The encoding LSI is fabricated using 0.25 micron four-layer metal CMOS technology and integrates 11 million transistors in an area of 14.2 mm 14.2 mm . The motion estimation LSI is fabricated using 0.35 micron three-layer metal CMOS technology. It integrates 1.9 million transistors in an area of 8.5 mm 8.5 mm . This chip set makes various system configurations possible and allows for a compact and cost-effective video encoder with high picture quality.

In this study, we prepared red organic light- emitting-diode (OLED) with a fluorescent dye(Sq)-doped and inserted 1,3-bis (5-p-t-butylphenyl)-1,3,4-oxadiazol-2-yl) benzene (OXD7) or/and tris (8-hydroxyquinoline) aluminum (Alq3) layers between emission layer and cathode in order to increase electroluminescent (EL) efficiency. This inserting effect has been observed and EL mechanism characteristics have been examined. The hole transport layer was N,N'-diphenyl-N, N'bis-(3-methylphenyl)-1,1'diphenyl-4,4'-diamine (TPD); the host material of emission layer was Alq3; the guest material of emission layer was Sq. When Alq3 was inserted between the emission layer and the cathode, emission efficiency increased. Highly pure red emission, however, was not attaina ble with Alq3. On the other hand, the insertion of OXD7 between the two layers blocked and accumulated holes. Because of its increasing recombination probability of electron and hole, luminance characteristics and emission efficiency were improved with holding highly pure red color.

This paper deals with the fundamental problem of automatic assessment of appearance of seam puckers on suits, and suggests possibilities for practical usage. Presently, evaluations are done by inspectors who compare standard photographs of suits to test samples. In order to avoid human errors, however, a method of automatic evaluation is desired. We process the problem as pattern recognition. As a feature we use fractal dimensions. The fractal dimensions obtained from standard photographs are used as template patterns. To make it easier to calculate fractal dimensions, we plot a curve representing the appearance of seam puckers, from which fractal dimensions of the curve can be calculated. The seam puckers in gray-scale images are confused with the material's texture, so the seam puckers must be enhanced for a precise evaluation. By using the concept of variance, we select images with seam puckers and enhance only the images with seam puckers. This is the novel aspect of this work. Twenty suits are used for the evaluation experiment and we obtain a result almost the same to the evaluation gained by inspection. That is, the evaluation of 11 samples is the same as that gained by inspection, the results of 8 samples differ by 1 grade, and the evaluation of 1 sample has a 2-grade difference. The results are also compared to the evaluation of the system using the Daubechies wavelet feature. The result of comparison shows that the present method gives a better evaluation than the system using the Daubechies wavelet.

The authors report ultra-high-speed digital IC modules that use 0.1-µm InAlAs/InGaAs/InP HEMTs for broadband optical fiber communication systems. The multiplexer IC module operated at up to 70 Gbit/s, and error-free operation of the decision IC module was confirmed at 50 Gbit/s. The speed of each module is the fastest yet reported for its kind.

We demonstrate unique dye-doping method to realize organic light emitting diodes (OLED) with high efficiency, high brightness and pure red emission. In this study, we used 5,10,15,20 tetraphenyl -21H,23H-porphine (TPP) as emitting dopant into 8-hydroxyquinoline aluminum (Alq3) emissive layer. To improve turn-on voltage and emission characteristics, a sufficient amount of 4-(dicyano methylene) -2-methyl -6-(p-dimethyl aminostyryl) -4H-pyran (DCM) was added to the TPP doped Alq3 emissive layer. The mechanisms and the emission characteristics of the co-doped EL device are discussed using energy band diagram of the materials used in the device.

To provide a bounded-delay service with an end-to-end delay guarantee and utilize network efficiently, the admission control functions in a network require an adequate per-switch delay allocation policy to allocate end-to-end delay requirement to a set of local switches. This letter present an optimal delay allocation policy, according to a deterministic traffic model, and a rate-controlled scheduler. Empirical results indicate that the proposed policy perform better than EQ allocation policy, using the admission load region as index.

In long-haul wavelength-division-multiplexed (WDM) transmission systems, signals with shorter and longer wavelengths have self-phase modulation group-velocity-dispersion (SPM-GVD) penalty caused by to the dispersion slope even after the dispersion-compensation at the receiver has been optimized. As a countermeasure, we have already proposed both pre-compensation and post-compensation of chromatic dispersion at the transmitter and receiver for each channel. This method can decrease the channel variation of path-averaged chromatic dispersion along the transmission line, and it can improve the eye opening of the waveform after transmission. We investigated the optimized parameter of chromatic dispersion and chirping at the transmitter. The optimized pre-dispersion compensation parameter R was about 50%. The optimized chirping parameter α was about 3 when the signal wavelength was less than the mean zero-dispersion wavelength. In a single-channel, 5.3-Gbit/s NRZ signal transmission experiment over a 4,760-km straight line, this method decreased SPM-GVD penalty. In a 32-channel, 5.3-Gbit/s WDM transmission experiment over 9,879 km using a circulating loop, this method improved Q-factors for the 1st and 32nd channels by more than 1.5 dB.

The k-mutual exclusion problem is the problem of guaranteeing that no more than k computing nodes enter a critical section simultaneously. The use of a k-coterie, which is a special set of node groups, is known as a robust approach to this problem. In general, k-coteries are classified as either dominated or nondominated, and a mutual exclusion mechanism has maximal availability when it employs a nondominated k-coterie. In this paper, we propose two new schemes called VOT and D-VOT for constructing nondominated k-coteries. We conduct a comparative evaluation of the proposed schemes and well-known previous schemes. The results clearly show the superiority of the proposed schemes.

A new method for measuring the scattering coefficient using a metal-plate reflector was developed in order to provide a non-destructive way for the assessment of microwave materials in free space. By displacing the position of the metal-plate reflector on the specimen to be tested, the incident wave and the scattered wave from the measured area were determined without the influence of extraneous waves such as the direct coupling between transmitting and receiving antennas and scattered waves from background objects. Because the behavior of a metal-plate reflector is similar to that of an optical shutter in optics, our new scattering measurement system enables us to measure both backward- and forward-scattering coefficients of small regions of the specimen for various types of materials in a non-destructive manner. Our study examined the metal-plate size dependence of the complex reflection and transmission coefficients of some dielectric sheet samples. The measured data indicated that the reflection and transmission coefficients of a Bakelite flat plate and Styrofoam sheet were constant for various sizes of metal plates at the X-band.

This paper presents a new method for statistical modelling of prosody control in speech synthesis. The proposed method, which is referred to as Constrained Tree Regression (CTR), can make suitable representation of complex effects of control factors for prosody with a moderate amount of learning data. It is based on recursive splits of predictor variable spaces and partial imposition of constraints of linear independence among predictor variables. It incorporates both linear and tree regressions with categorical predictor variables, which have been conventionally used for prosody control, and extends them to more general models. In addition, a hierarchical error function is presented to consider hierarchical structure in prosody control. This new method is applied to modelling of speech segmental duration. Experimental results show that better duration models are obtained by using the proposed regression method compared with linear and tree regressions using the same number of free parameters. It is also shown that the hierarchical structure of phoneme and syllable durations can be represented efficiently using the hierarchical error function.

Mobile computing networks make it possible to offer information access to mobile users. In order to transfer data over mobile networks efficiently, appropriate data transmission control methods for mobile terminals must be established. This paper focuses on spot communication systems to transmit data at high speeds between base stations and mobile terminals. It proposes a flexible and efficient data transmission method that is suitable for spot communication systems. The proposed method transfers subsets of the data to the base stations that are best sited relative to the mobile terminal. This helps to reduce the traffic load of the network significantly. Simulation results confirm the validity of the proposed method. Furthermore, the data receiving time of the mobile terminal, which is an important measure in evaluating the Quality of Service (QoS) for data transmission is analyzed. The result shows that the traffic load in the network is reduced significantly while the QoS is well maintained.

Site diversity causes unfairness in packet reception that depends on the location of the mobile stations in the up-link of CDMA cellular packet communication systems. This paper proposes an adaptive transmit permission probability control scheme that reduces this unfairness in CDMA cellular slotted-ALOHA systems with site diversity. The proposed scheme adaptively controls the transmit permission probability according to the offered load and the location of the mobile stations. Successful packet reception rate, fairness coefficient and throughput performance are evaluated in fading environments with imperfect power control. Computer simulation shows that adaptive transmit permission probability control improves fairness of service for all mobile stations and throughput performance across all channel loads compared with the conventional scheme.