Microstructure and analysis of oxide scales formed on Cr-Si-Ni compacts in air and H2O-containing atmosphere

The purpose of this study was to characterize the oxide scales formed on various Cr-Si-Ni compacts at 1273 K in air and H₂O-containing atmosphere by TEM. It was found that CrSi₂-(5-20)mass%Ni compacts form double layer scales, consisting of an outer Cr₂O₃ layer and an inner SiO₂ layer. The oxide scale changed from SiO₂- to Cr₂O₃-based scale with an increase in the Ni concentration. However, it was observed that the oxide scale formed in H₂O-containing atmospheres showed local SiO₂ growth into the substrate. This result suggests that the inward oxidant diffusion promotes the local growth of SiO₂ in the H₂O-containing atmospheres.     

Analysis of Polarization Splitters Composed of Multilayer Thin-Film Waveguides Using the Beam-Propagation Method Based on Yee's Mesh

Multilayer thin-film waveguides (MTFWs) are analyzed using the beam-propagation method based on Yee's mesh. The birefringence properties of the MTFW are demonstrated by the eigenmode analysis based on the imaginary-distance procedure. Taking advantage of the birefringence, a polarization splitter composed of two parallel MTFWs is proposed. Calculation shows that a short device length of 270 mum is obtainable with crosstalks of -33.5 dB for the quasi-transverse-electric mode and -20.7 dB for the quasi-transverse-magnetic mode. A crossing-type polarization splitter is also developed, and the device length is further reduced to 120 mum.     

A cavity-backed rectangular aperture antenna with application to a tilted fan beam array antenna

A rectangular aperture of A/sub x//spl times/A/sub y/, cut in the top conducting plate of a triplate transmission line and backed by a cavity, radiates a tilted beam off the direction normal to the aperture. The mechanism of the radiation is explained using the Poynting vector distribution above the aperture and the phase distribution of the electric field over the aperture. The tilt angle is calculated as a function of side length A/sub x/ for a representative value of A/sub y/=18 mm=0.747/spl lambda//sub 12.45/, where /spl lambda//sub 12.45/ is the wavelength at a test frequency of 12.45 GHz. A tilted beam of approximately 27/spl deg/ is realized at A/sub x//A/sub y/=8/9 with a gain of approximately 8 dB. Using this value of A/sub x//A/sub y/, an array antenna composed of rectangular cavity-backed aperture elements is investigated. The array forms a tilted fan beam without phase shifters. The frequency responses of the gain and input impedance are discussed.     

Design methodology of embedded DRAM with virtual-socketarchitecture

This paper proposes the virtual-socket architecture in order to reduce the design turn-around time (TAT) of the embedded DRAM. The required memory density and the function of the embedded DRAM are system dependent. In the conventional design, the DRAM control circuitry with the DRAM memory array is handled as a hardware macro, resulting in the increase in design TAT. On the other hand, our proposed architecture provides the DRAM control circuitry as a software macro to take advantage of the automated tools based on synchronous circuit design. With array-generator technology, this architecture can achieve high quality and quick turn-around time (QTAT) of flexible embedded DRAM that is almost the same as the CMOS ASIC. We applied this virtual-socket architecture to the development of the 61-Mb synchronous DRAM core using 0.18-μm design rule and confirmed the high-speed operation, 166 MHz at CAS latency of two, and 180 MHz at that of three. The experimental results show that our proposed architecture can be applied to the development of the high-performance embedded DRAM with design QTAT     

Comparative study of absorbing boundary conditions for thetime-domain beam propagation method

Various absorbing boundary conditions (ABCs) are compared in the analysis of the time-domain finite-difference beam propagation method. For a one-dimensional problem, the following ABCs are tested: Higdon's absorbing boundary, Ramahi's complementary operators method (COM), its concurrent version (C-COM) and Berenger's perfectly matched layer (PML). It is found that the second- and third-order C-COMs with three and four boundary cells are comparable to the PMLs with eight and 16 cells, respectively. The effectiveness of the C-COM is also discussed in a two-dimensional problem     

Low-profile helical array antenna fed from a radial waveguide

A low-profile array antenna composed of two-turn 4° pitch angle helices is designed for a frequency band of 11.7 GHz to 12.0 GHz. The feed wire of each helix is inserted into a radial waveguide through a small hole and excited by a traveling wave flowing in the transverse electromagnetic mode between the two parallel plates of the waveguide. The measured aperture efficiency shows a maximum value of 77% for a beam radiated in the normal direction and 69% for a 30° beam tilt     

Real-time 3-D model-based navigation system for endoscopicparanasal sinus surgery

This paper presents a three-dimensional (3-D)-model-based navigation system for endoscopic sinus surgery treating paranasal sinusitis. Endoscopic surgery is becoming more common because of its low invasiveness. Its problem with disorientation, however, is one of the toughest barriers for the novice and may lead even an expert to commit serious surgical errors, e.g., causing cerebrospinal fluid (CSF) leakage or blinding the patient. To prevent such complications and optimize training, the authors' system aids in navigation by showing a single perspective view of the patient and the endoscope models. This virtual endoscope has a viewing cone with a simulated light to indicate the viewing direction and visual field in real-time. The system's three clipping planes automatically follow the endoscope and help keep the surgeon aware of the endoscope's actual position. An experiment comparing the system to conventional navigation using a triplanar display showed that the perspective view was referenced very frequently, giving a positive impressions, while the triplanar display was almost completely ignored, apparently because it was too difficult to interpret immediately     

Interactive multimedia communication systems for next-generationeducation using asymmetrical satellite and terrestrial networks

We propose a new concept of a hierarchical network structure for remote education. This system combines broadband satellite networks and simple terrestrial communication networks effectively to meet the demands of point-to-multipoint communications. Remote education experiments have been conducted using the proposed satellite communication networks. The results of network characteristics and degree of satisfaction are discussed. Acceptable communication quality was achieved ensuring an interactive lecture environment     

High-performance embedded SOI DRAM architecture for the low-powersupply

This paper presents the high-performance DRAM array and logic architecture for a sub-1.2-V embedded silicon-on-insulator (SOI) DRAM. The degradation of the transistor performance caused by boosted wordline voltage level is distinctly apparent in the low voltage range. In our proposed stressless SOI DRAM array, the applied electric field to the gate oxide of the memory-cell transistor can he relaxed. The crucial problem that the gate oxide of the embedded-DRAM process must be thicker than that of the logic process can be solved. As a result, the performance degradation of the logic transistor can be avoided without forming the gate oxides of the memory-cell array and the logic circuits individually. In addition, the data retention characteristics can be improved. Secondly, we propose the body-bias-controlled SOI-circuit architecture which enhances the performance of the logic circuit at sub-1.2-V power supply voltage, Experimental results verify that the proposed circuit architecture has the potential to reduce the gate-delay time up to 30% compared to the conventional one. This proposed architecture could provide high performance in the low-voltage embedded SOI DRAM     

Electromagnetically coupled curl antenna

The radiation characteristics of a curl antenna excited by an L-wire are presented. The frequency bandwidth for a 3 dB axial ratio criterion is ~6%, with a nearly resistive input impedance of 75 Ω. An array antenna of the 36 curls shows a gain of 23 dB with an aperture efficiency of 73%