At the sliding contact of brush and rotating slip-ring or commutator, it has been recognized that the brush wear is influenced by brush pressure, current density and atmosphere nearby contact part. However, little is known about the relation between brush wear and atmosphere condition in detail. In this paper, the experiments are carried out with a great attention to the effect of surrounding temperature and humidity on brush wear. The sliding part of brush and slip-ring is put on the sealed box and the atmosphere in the sealed box is kept on the specified condition by temperature and humidity control system. The brush wear, contact voltage drop and slip-ring surface morphology are observed after the sliding test. From these results, in both cases of the high humidity (nearby 80%) and low humidity (nearby 20%), the brush wear are large. And the brush wear rate is the lowest around 60% relative humidity. However, the characteristics of brush wear under the 15C is not similar to others. When the surrounding temperature is changed, in case of the 20% humidity, the brush wear increases with increasing surrounding temperature. On the other hand, in case of 80% humidity, the brush wear increases with decreasing surrounding temperature. Consequently, the results clearly shows that the temperature and humidity not only affect the brush wear but also change the condition of the film formation on slip-ring.

Future high density magnetic recording requires a nanometer spaced head-slider interface, high track seeking velocity and high spindle speed. Such a combination greatly increases the likelihood of slider-disk and slider-particle-disk impact. Furthermore, the impact can generate high flash temperature and leads to data reliability problems, such as partial or full data erasure. This work report a method to conduct controlled experimental investigations into the possibility of such a data erasure even when the temperature is far below the Curie temperature. Results indicate that the high density magnetic transitions are of high likelihood of being affected by the flash temperature. Investigations also extended to micromagnetic modeling of the flash temperature effect. Results suggest that thermally induced local stress can play important roll in the data erasure process. Modeling results also exhibit that smaller grain size and higher recording density are also of higher likelihood of getting the transitions being affected by the flash temperature.

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 paper the application of a linear-quadratic processor is proposed for detection of each user's signal in a direct sequence code division multiple access scheme and, in particular, for W-CDMA systems. In this method, the knowledge of the user of interest, and some statistical knowledge of interfering transmitters' signals are used to detect the desired user's signal without needing exact "a priori" knowledge of the interfering signal parameters such as spreading sequences and signal powers. Parameters of the proposed processor, which are derived so as to maximise the signal-to-interference-plus-noise ratio (SINR), can generally be obtained by solving a system of linear equations for which many effective techniques exist. A model for this detection procedure is developed and shown--through analytical and numerical results--to offer a good compromise between complexity and quality of performance.

In order to serve traffic hot spots, the hierarchical cellular systems or the hybrid TDMA/CDMA have been proposed, recently. In order to depress the multi-user interference and increase capacity, the forward link power control strategy is adopted in the macrocell/microcell hierarchical cellular system using code division multiple access (CDMA). Its effects are estimated in this paper. Especially, the impact of -th distance power control laws on the forward link outage probability and capacity plane for the hierarchical cellular system are investigated. The coverage area user capacity of the overlaid macrocell/microcell cellular system is obtained. The numerical results and discussions with previous published results are presented in detail.

Numerical modeling of realistic engineering problems using the FDTD technique often requires smaller cell size, higher simulation accuracy and less computation resources. In this paper, we describe a high performance three-dimensional FDTD algorithm by using non-uniform mesh that allows flexible cell size to improve the accuracy of modeling, and computation resource also can be reduced greatly. In this paper, we will first explain the detailed formulation and algorithm of Non-Uniform Mesh. Next, examination of the reflection error from fine-coarse boundary because of the discontinuity is carried out. Then some test geometry are solved by using both uniform mesh and non-uniform mesh FDTD scheme to validate the results and check the accuracy of solution. We also examine the calculation accuracy due to mesh size ratio, and then investigation of how to determine the fine mesh region surrounding the object for a most small computation error will be carried out in this paper. In addition, the algorithm is demonstrated for several different antenna geometry.

In this paper, using a standard propagation model, the performance evaluation of a code-division-multiple-access (CDMA) cellular system with high data rate services for the reverse and forward links is investigated. In the approach, we propose "Equivalent Load" to estimate two cases of the system termed as the static analysis and the dynamic analysis. Performance measures of the static analysis obtained include the system capacity plane, outage probability and throughput. Performance measures of the dynamic analysis obtained include the allowed maximum data rate and the constraint set between the load situation and the data rate. We also estimate the effects of the power control on the system.

Software radio or software defined radio (SDR) is a quite attractive field of research in terms of theoretical cross-over research themes between radio engineering and computer science in academia as well as new multi-standard or all-purpose radio system products in industry. In order to promote research and development in a field of SDR this paper briefly introduces some prospective aspect and research themes on SDR. There are many approaches to research SDR such as architectures, devises, algorithms, description languages and API (application program interface) for achieving reconfigurability and downloadability in an SDR system. One of the approaches is to focus on an antenna for SDR. Although a baseband circuit is generally programable and reconfigurable, an antenna and a RF circuit are used to be less flexible and hardware-dependent and then result in a bottleneck for implementing an SDR system. However, an adaptive array antenna or a smart antenna named a software antenna is adaptively controllable and reconfigurable because it can be programable to form a desired beam pattern if an appropriate set of antenna weights is provided with software. It must be a vital tool for carrying out an SDR system. A software antenna can be considered as an adaptive filter in space and time domains for radio communications, so that the communication theory can be generalized from a conventional time domain into both space and time domains. This paper also introduces structures and theories of a software antenna which I have been studying before this millennium.

This paper discusses and clarifies effectiveness of data-driven implementation of protocol handling system to access TINA (Telecommunications Information Networking Architecture) network and internet. TINA is a networking architecture that achieves networking services and management ubiquitously for users and networks. Many TINA related ACTS (Advanced Communication Technologies and Services) projects have been organized in Europe. In Japan, The TINA Trial (TTT) to achieve ATM network management and services based on TINA architectures was done by NTT and several manufactures from April 1997 to April 1999. In these studies and trials, much effort is devoted to development of software based on service architecture and network architecture being standardized in TINA-C (TINA Consortium). In order to achieve TINA environment universally in customers and network sides, we have to consider how to deploy TINA environment onto user side and how to use access transmission capacity as efficiently as possible. Recent technology can easily achieve application and environment downloading from the network side to user side by use of e. g. , JAVA. In accessing the network, there are several possible bottlenecks in information exchange in customer side such as PC processing capability, access protocol handling capability, intra-house wiring bandwidth. Authors, in parallel with TINA software architecture study, have been studying versatile requirements for hardware platform of TINA network. In those studies, we have clarified that the stream-oriented data-driven processor authors have been studying and developing have high reliability, high multiprocessing and multimedia information processing capability. Based on these studies, this paper first shows Von Neumann-based protocol handler is ineffective in case of multiprocessing through mathematical and emulation studies. Then, we show our data-driven protocol handling can effectively realize access protocol handling by emulation study. Then, we describe a result of first step of implementation of data-driven TCP/IP protocol handling. This result proves our TCP/IP hub based on data-driven processor is applicable not only for TINA/CORBA network but normal internet access. Finally, we show a possible customer premises network configuration which resolves bottleneck to access TINA network through ATM access.

In this letter, we describe a four thin-film-transistor (TFT) pixel circuit based on hydrogenated amorphous silicon (a-Si:H) technology for the active-matrix organic light-emitting diode (AMOLED) display applications. The circuit uses current-writing mechanism and can automatically adjust the threshold-voltage shifts of both the organic light-emitting diodes (OLEDs) and the TFTs induced by the circuit aging or process variations. Experimental results indicate virtually no variation of the output driving current after long-term bias-temperature-stress (BTS).

This paper proposes a novel cache architecture suitable for merged DRAM/logic LSIs, which is called "dynamically variable line-size cache (D-VLS cache). " The D-VLS cache can optimize its line-size according to the characteristic of programs, and attempts to improve the performance by exploiting the high on-chip memory bandwidth on merged DRAM/logic LSIs appropriately. In our evaluation, it is observed that an average memory-access time improvement achieved by a direct-mapped D-VLS cache is about 20% compared to a conventional direct-mapped cache with fixed 32-byte lines. This performance improvement is better than that of a doubled-size conventional direct-mapped cache.

A new output driver design called modified asymmetrical slew rate (MASR) output driver was proposed to reduce the simultaneous switching noise without sacrificing switching speed, for high speed and heavy loading applications. The driving capability of the output driver was designed to sink/source 64 mA current @ VOL/VOH = 0.4 V/4.6 V, with 66 pF and 50 Ω loading. When four drivers switch simultaneously, the ground bounce was design to be less than 0.8 V. The performances of the conventional, controlled slew rate (CSR), and MASR output drivers were analyzed by computer simulation. These three types of drivers were implemented with a 0.8 µm CMOS process. The measured ground bounce of the conventional driver is 1.22 V, while the ground bounce of the MASR driver is reduced to 0.72 V. The propagation delays of the conventional and MASR drivers are the same. The performance of the MASR driver is better than that of the CSR driver in all aspects.

The epitaxial lateral overgrowth (ELO) of GaN with a stripe tungsten (W) mask pattern is performed by hydride vapor phase epitaxy (HVPE) and the crystalline and optical properties are investigated compared with ELO GaN using SiO2 mask by characterizations of X-ray rocking curve (XRC), transmission electron microscopy (TEM) and low temperature cathodoluminescence (CL). A buried ELO structure of the W mask with a smooth surface is successfully obtained. The tilt of c-axis on the W mask in the ELO GaN is not observed, but in the case of the SiO2 mask, c-axis tilts on the mask region at 1 to 10 together with small angle grain boundaries. Half the way from the ELO interface to the surface, the luminescence becomes excitonic over the whole lateral extension region, which indicates the optically high crystalline quality of the material. On the other hand, different kinds of luminescence are observed depending on the position. The difference of these luminescence is caused by the defects and/or impurity incorporation on the mask region due to the tilting of c-axis.

Electron-cyclotron-resonance plasma-excited molecular beam epitaxial (ECR-MBE) growth of GaN using hydrogen-nitrogen mixed gas plasma was investigated. The growth rate of GaN was drastically increased by addition of hydrogen to nitrogen plasma. The transition of reflection high energy electron diffraction (RHEED) patterns, from streaked patterns created without the presence of hydrogen to spotted patterns in the presence of hydrogen, indicated that the effective V/III ratio was increased by the addition of hydrogen. NHx radical families were detected in hydrogen-nitrogen mixed gas plasma by quadrupole mass spectroscopy and optical emission spectroscopy. These radicals were considered to be responsible for the observed increase in growth rate. Transmission electron microscope observation showed that the surface morphology of GaN without hydrogen was relatively flat and that with hydrogen was columnar with {1 0 ~1 1} facets. It seems likely that the columnar structure of the GaN layers grown with hydrogen were strongly related to initial island growth.

This note investigates the characterizing properties of the level sets of an M-convex function introduced by Murota.

An improvement of the fiber-optic transceiver having both transmitter and receiver functions of optical time-domain reflectometers is examined. The improvement is achieved by introducing an external optical amplifier without changing the previously reported configuration. The characteristics of the transmitted Q-switched pulse and the receiver gain is studied theoretically and experimentally to estimate the performance improvement. It is found that the introduction of the external optical amplifier is a simple and effective way to the performance improvement.

Triangulations have been one of main research topics in computational geometry and have many applications in computer graphics, finite element methods, mesh generation, etc. This paper surveys properties of triangulations in the two- or higher-dimensional spaces. For triangulations of the planar point set, we have a good triangulation, called the Delaunay triangulation, which satisfies several optimality criteria. Based on Delaunay triangulations, many properties of planar triangulations can be shown, and a graph structure can be constructed for all planar triangulations. On the other hand, triangulations in higher dimensions are much more complicated than in planar cases. However, there does exist a subclass of triangulations, called regular triangulations, with nice structure, which is also touched upon.

Characteristics of an FBG hydrophone are described under various conditions. The developed FBG hydrophone detects an acoustic field in water with good performances: linear response,high sensitivity,high stability,wide dynamic range as large as 90 dB and wide operation frequency range from a few kHz to a few MHz. A WDM FBG hydrophone consisting of two FBGs in serial connection can detect simultaneously amplitudes and phases of acoustic fields at different points,which in turn allows a directive measurement of an acoustic field in water.

Given a plane graph G, we wish to find a drawing of G in the plane such that the vertices of G are represented as grid points, and the edges are represented as straight-line segments between their endpoints without any edge-intersection. Such drawings are called planar straight-line drawings of G. An additional objective is to minimize the area of the rectangular grid in which G is drawn. In this paper first we review known two methods to find such drawings, then explain a hidden relation between them, and finally survey related results.

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.