Microstructure Development and Dielectric Properties of Potassium Strontium Niobate Ceramics

Sintering of a KSr₂Nb₅O₁₅ powder compact at 1350°C resulted in a duplex structure. Prefiring of the compact between 1200° and 1300°C inhibited the abnormal grain growth responsible for the duplex structure. The Curie temperature and dielectric constant were dependent on the microstructure.     

Ceramic Dental Molds for the Precision Casting of Titanium and Titanium Alloys: I, Relationship between Particle-Size Distribution of Aggregates and Mold Expansion

A new ceramic dental mold can cast excellent Ti restoratives by controlling expansion due to the oxidation of additive metal particles. The packing structure of the metal and aggregate particles in the mold can be considered a function of the size distribution of the aggregate grains. An investigation of the expansion mechanism reveals three different relationships of void fraction versus linear thermal expansion for the molds at the high temperature under which oxidation of the metal particles occurs. Room-temperature casting, favorable for making high-quality Ti restoratives, can also be achieved by precisely controlling both the amount of additive metal powder and the compositional distribution of aggregate grain sizes in the mold.     

Design of low‐power all‐optical networks under the constraint of four‐wave mixing

In this paper, we propose a static lightpath establishment method to design low‐power all‐optical networks under the constraint of four‐wave mixing (FWM). Since the FWM causes nonlinear interchannel crosstalk, it degrades the communication quality of optical signals. The FWM crosstalk effect becomes strong in a fiber as the number of passing optical signals increases. Therefore, we should reduce the number of optical signals passing through the same fiber from the perspective of the FWM. Meanwhile, in order to enhance the power efficiency of optical amplifiers, which are deployed at each optical fiber, it is preferred that multiple optical signals are transmitted in the same fiber. In order to decrease the power consumption while keeping high communication quality, the proposed method statically selects routes, wavelengths, and fibers for each traffic demand, considering the FWM crosstalk effect and the usage efficiency of the optical amplifiers. We show the performance of the proposed method through numerical experiments.     

Suppressive Fair Buffer Management Policy for Intermittently Connected Mobile Ad Hoc Networks

Wireless Personal Communications - We propose a suppressive fair buffer management policy for intermittently connected mobile ad-hoc networks. So far, several buffer management policies have been...     

Fabrication of MOD-derived YBCO films on [001]LaAlO/sub 3/ and their application to /spl lambda//4 CPW SIR BPFs

Chemically derived epitaxial thin films of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) are fabricated on [001]LaAlO/sub 3/ substrates by the metalorganic-deposition (MOD) process, which has advantages of high quality, nonvacuum, low-cost, and large-scale production of high-T/sub c/ superconducting films. The MOD-derived YBCO films have a sharp transition at the critical temperature (90.4 K) and a high-quality film with a surface resistance of 0.13 m/spl Omega/ (30 K, 9.98 GHz) is obtained. As a microwave application, simple and compact bandpass filters (BPFs) using /spl lambda//4 coplanar-waveguide. stepped-impedance resonators are demonstrated on the YBCO films. A two-stage Chebyshev BPF of center frequency of 5.731 GHz, bandwidth of 135 MHz, and insertion loss of 0.29 dB with little input power dependency in a power range less than 10 dBm is realized on the film.     

A low-impedance open-bitline array for multigigabit DRAM

The noise-generating mechanisms inherent in the open-bitline DRAM array using the 6F² (F: feature size) memory cells and techniques for reducing the noise are described. The sources of differential noise coupled to the paired bitlines laid out in two arrays are the p-well, cell plate, and the group of nonselected wordlines. It was found, by simulation and by experiment with a 0.13-μm 256-Mb test chip, that the level of noise is dramatically reduced by using a low-impedance array with careful layout featuring low-resistivity materials, tight bridging between pairs of adjacent arrays, and a small array, achieving a comparable level of noise to that seen in the twisted and folded-bitline array. On basis of these results, it turns out that the open-bitline array has a strong chance of revival in the multigigabit generation, as long as these noise reduction techniques are applied     

Purification and characterization of the Clostridium josui porphobilinogen deaminase encoded by the hemC gene from a recombinant Escherichia coli

The porphobilinogen deaminase encoded by the Clostridium josui hemC gene was purified from a recombinant Escherichia coli strain and its properties were characterized. The optimal temperature and pH of the purified enzyme were 65 degrees C and 7.0, respectively. This enzyme was quite thermostable: it retained 86% of the original activity after incubation at 70 degrees C for 1 h. The Km and Vmax values of the enzyme were 65 microM and 3.3 micromol/h/mg for porphobilinogen, respectively.     

Optical loss increase in optical fibre coated with silicone resin containing Si?D

One possible origin of the loss increase phenomenon with heat treatment at 200°C (H2 evolution from the coating material) has been investigated, using optical fibre coated with silicone resin containing the Si?D group. Although OH absorption at 1.4 ?m increases with 200°C heat treatment, no OD peak is observed. It is suggested that silicone resin containing no Si?H and Si?CH2?CH2?Si groups is appropriate as a coating material as no H2 evolution is present.     

Light modulator using piezoelectric films with waveguides

A light modulator using piezoelectric films based on optical interference of the Mach-Zehnder type has been proposed and demonstrated. The modulator is constructed with two optical waveguides joined to each other at both ends to divide the incident light and to recombine them, and each waveguide is fabricated on a polyvinylidene fluoride (PVDF) film to serve as a voltage-driven phase-shifter.     

Low-power chip interconnection by dynamic termination

A low-power dynamic termination scheme is proposed and demonstrated as a way to reduce power dissipation for high-speed data transport. In this scheme, the transmission lines are terminated only if the signals change. The gate of a switching MOS transistor connected to a termination resistor is driven by differentiating the transmission signal with a resistor and a capacitor. The power dissipation of the terminating resistor can be reduced to 1/5 in the conventional determination scheme, and overshoot can be reduced to 1/5 that in the open scheme. This scheme is promising for use with palm-top equipment, facilitating high-speed low power operation