In situ polyurethane/silica composite formation via a sol‐gel process

Polyurethane acrylate anionomer (PUAA)/silica composite gels were prepared by the sol‐gel reaction of tetraethoxysilane (TEOS) and methacryloxypropyl trimethoxysilane (MPTS) incorporated to PUAA gels by using a swelling method. The formation and structure of composites were confirmed by FTIR, X‐ray diffraction, and SEM. As a result, we found that silica components in composites are located within the ionic domains of their gels and interacted with PUAA via hydrogen bonding. This drastically enhanced the mechanical properties of the composites. Mechanical properties are also improved by MPTS, because MPTS improves the dispersibility and adhesion of silica components in PUAA/silica composite gels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2327–2334, 2002     

Development of a thermal hydraulic analysis code for gas-cooled reactors with annular fuels

Gas-cooled reactors have been highlighted as a promising option for next generation reactor technology. A thermal hydraulic analysis code for gas-cooled reactors has been developed with a heat transfer model of a block element, which is solved implicitly with the helium energy equation. Validation was carried out through comparison with both experimental and analytical results. A computation module for annular fuel rods has been coupled to the code for comparative analyses of an annular fuel-based block element. At normal operation, the annular fuel shows 80 °C lower peak temperature than the solid fuel for the same power in Japan's high temperature engineering test reactor (HTTR), even though the pressure drop is higher in the annular fuel.     

Experimental observations on flow characteristics in an open two-phase natural circulation loop

The flow behavior in an open two-phase natural circulation loop was studied experimentally using Freon-113. The heat flux, inlet- and exit-restrictions, liquid charging level and inlet subcooling were taken as parameters. As a result, three basic circulation modes were observed with variation of the heat flux: periodic circulation (A), continuous circulation, and periodic circulation (B). Of these modes, only the continuous circulation mode was stable and the maximum circulation rate appeared with this mode. An increase in the inlet-restriction and/or decrease in the exit-restriction broadened the range of the continuous circulation mode and stabilized the system. When the liquid charging level was lowered or the inlet subcooling was decreased, the continuous circulation mode started at a lower heat flux and the system became stable. The results are summarized on instability maps in the plane of heat flux vs. inlet subcooling.     

Decision-directed maximum-likelihood estimation of OFDM framesynchronisation offset

The authors propose a method to estimate the synchronisation offset for orthogonal frequency division multiplexing (OFDM) frame alignment without resort to pilot tones. A decision-directed maximum-likelihood estimation of frame synchronisation offset is derived, and the performance of the proposed scheme is confirmed by computer simulation for QAM systems     

Classification of pixels in a noisy grayscale image of polar ice

Often, in synthetic aperture radar (SAR) images of polar ice, one encounters shadow-like features across the images. Such features make it difficult to classify pixels into ice and water. Accordingly, it becomes a challenge to determine the true size and boundaries of ice floes in an SAR image of polar ice. We develop a simple statistical procedure which classifies pixels of an image by eliminating the effects of shadow-like features. Methodology developed in this paper is illustrated using some noisy SAR images of ice floes in the Arctic sea.     

Physical model of drain conductance, gd, degradation ofNMOSFET's due to interface state generation by hot carrierinjection

Degradation of analog device parameters such as drain conductance, g_d, due to hot carrier injection has been modeled for NMOSFET's. In this modeling, mobility reduction caused by interface state generation by hot carrier injection and the gradual channel approximation were employed. It has been found that g_d degradation can be calculated from linear region transconductance, g_m, degradation which is usually monitored for hot carrier degradation of MOSFET's. The values of g_d degradation calculated from g_m degradation fit well to the measured values of g_d degradation The dependence of the g_d degradation lifetime on L_eff has been also studied, this model also provides an explanation of the dependence on L_eff. The model is then useful for lifetime predictions of analog circuits in which g_d degradation is usually more important than g_m degradation     

Integration of mobile vehicles for automated material handlingusing Profibus and IEEE 802.11 networks

This paper focuses on a method to integrate mobile devices such as a mobile robot, automated guided vehicle, and unmanned container transporter to form an automated material handling system. In this paper, the stationary devices are connected via a Profibus network while the mobile devices are communicating via an IEEE 802.11 wireless LAN. In order to integrate these two networks, a protocol converter is developed on a PC platform that runs two interacting processes with shared internal buffers. The protocol converter performs a role of translator between two different protocols by converting the format of a data frame. In addition to this basic conversion function, the protocol converter has a virtual polling algorithm to reduce the uncertainty involved in accessing the wireless network. Finally, the integrated network. of Profibus and IEEE 802.11 is experimentally evaluated for its data latency and throughput, which shows the feasibility of the Profibus-IEEE 802.11 network for industrial applications involving mobile devices     

Effect of lanthanide ions on the phase behavior of dipalmitoylphosphatidylcholine multilamellar liposomes

The effect of lanthanide ions (Ln3+) and their coordination compounds of diethylenetriamine pentaacetic acid (DTPA) on the phase behavior of dipalmitoylphosphatidylcholine (DPPC) multi-lamellar liposomes has been studied by differential scanning calorimetry (DSC), Raman spectroscopy, and freeze-fracture electron microscopic techniques. The displacement of Ca2+ binding on DPPC liposomes by lanthanide ions was also studied. The results show that the binding degree of four kinds of chloride salts with DPPC liposomes is: YbCl3 > GdCl3 > LaCl3 > CaCl2. Lanthanide ions increase the phase transition temperature of DPPC liposomes and decrease the membrane fluidity. Freeze-fracture electron microscopic results show that La3+ enhances the order of DPPC membrane. The effect of coordination compounds of lanthanides with DTPA on the phase behavior of DPPC liposomes is smaller than that of their chlorides. La3+, Gd3+, and Yb3+, can displace Ca2+ binding on DPPC liposomes, but there coordination compounds of DTPA can hardly displace Ca2+. Raman spectroscopic results show that a very slight effect in lateral packing order of DPPC liposomes was observed at various concentrations of lanthanides.     

A new MMIC broadside coupler using an array of air-bridges for directivity enhancement

A new quadrature broadside coupler is proposed, which employs an array of air-bridges to enhance directivity via its phase-equalization effect on the c-mode and /spl pi/-modes. The realization of air-bridges follows a standard MMIC fabrication process. An experimental chip fabricated on the 75-/spl mu/m GaAs substrate verifies the air-bridge effect and shows wideband characteristics of the coupling of 3.2/spl plusmn/0.4 dB, the insertion loss of 3.9/spl plusmn/0.4 dB, the output phase deviation from quadrature less than 6/spl deg/, and the isolation greater than 18 dB from 20 to 40 GHz.     

Test data compression and test time reduction using an embedded microprocessor

Systems-on-a-chip (SOCs) with many complex intellectual property cores require a large volume of data for manufacturing test. The computing power of the embedded processor in a SOC can be used to test the cores within the chip boundary, reducing the test time and memory requirements. This paper discusses techniques that use the computing power of the embedded processor in a more sophisticated way. The processor can generate and reuse random numbers to construct test patterns and selectively apply only those patterns that contribute to the fault coverage, significantly reducing the pattern generation time, the total number of test applications and, hence, the test time. It can also apply deterministic test patterns that have been compressed using the characteristics of the random patterns as well as those of the deterministic patterns themselves, which leads to high compression of test data. We compare three fast run-length coding schemes which are easily implemented and effective for test-data compression. We also demonstrate the effectiveness of the proposed approach by applying it to some benchmark circuits and by comparing it with other available techniques.