Compact long-period grating module with multi-attenuation peaks

A compact long-period grating (LPG) module with multiattenuation peaks has been successfully developed. The module has a simple design and is based on exploiting the coupling between the core mode and the different cladding modes for each peak. 43 mm long LPG modules have been fabricated and their temperature dependence measured     

Resonator fiber optic gyro using digital serrodyne modulation

A resonator fiber optic gyro using digital serrodyne modulation for control the input lightwave frequency is proposed. In the system, phase modulators in an integrated waveguide circuit are used, instead of an acousto-optical modulator (AOM) frequency shifters with bulky shapes. With operating the signal digitally, it becomes easy to track the resonant frequency by the feedback with a higher accuracy. Errors due to nonideal digital serrodyne waveform are analyzed and are shown to be small enough. Performances of this system are experimentally demonstrated, under open-loop and closed-loop operation. The proposed scheme can implement the ways to reduce the noises without increasing the number of optical elements     

Deposition-temperature dependence of structure,ferroelectric property and conduction mechanism of BCZT epitaxial films

Ba_0·85Ca_0·15Zr_0·1Ti_0·9O₃ (BCZT) epitaxial films were successfully deposited on (001) Nb-doped SrTiO₃ substrate, and the effects of deposition temperatures on the structure, ferroelectric property, and conduction mechanism were studied. The results of XRD and AFM verified the well epitaxial structure with smooth surfaces of the deposited BCZT epitaxial films. BCZT epitaxial films deposited at 650 °C exhibited the best ferroelectric property (2P_r = 22.91 μC/cm², 2E_C = 1702.11 kV/cm) and relatively low leakage current density (7.91 × 10³ A/cm²). The conduction mechanism of BCZT films corresponds to the space-charge-limited current (SCLC) mechanism and the Fowler-Nordheim (F–N) tunneling mechanism in the low and high electric field range, respectively.     

The effect of interface roughness on the perpendicular exchange bias of NiO/CoPt/Pt stacking structure

An orthogonal coupling structure of Ni O/Co Pt/Pt/glass with perpendicular exchange bias effect has been prepared. The exchange bias is found to be strongly dependent on the interface roughness between Ni O and Co Pt layer. The conventional inverse proportionality of the exchange bias field with the ferromagnetic thickness is not applicable to this top-pinned stacking structure.Moreover, an anomalous ferromagnetic thickness dependence of blocking temperature is also observed. A simulation on the basis of a spin configuration model with defects at the interface agrees well with the experimental observations. These findings suggest considerable contribution of the interface roughness to the perpendicular exchange bias.     

Effect of substrate temperature on the structure and magnetic properties of CoPt/AlN multilayer films

The effect of substrate temperature on the structure and magnetic properties of CoPt/AlN multilayer films has been investigated.The crystallinity of CoPt has been improved with increasing substrate temperature from room temperature to 400 ℃.After post-annealing process,L1_0 CoPt structure transformation has also been promoted.However,since the easy magnetic axis of L1_0 CoPt is in[001]orientation,the promotion of L1_0 CoPt transformation causes the change of easy magnetic axis in(111) textured CoPt layers,which impairs the perpendicular magnetic anisotropy.The optimum substrate temperature should be room temperature to obtain the strongest perpendicular magnetic anisotropy according to the results of the present work.     

Database migration: a new architecture for transaction processingin broadband networks

Due to recent developments in network technologies, broader channel bandwidth is becoming prevalent in worldwide networks. As one of the new technologies making good use of such broadband channels, dynamic relocation of databases through networks, database migration, will soon be used in practice as a powerful and basic database operation. We propose two transaction processing methods to take advantage of database migration in broadband networks. These methods choose the most efficient transaction processing method between the conventional method, based on the two-phase commit protocol, and our method, using database migration. We also propose a concurrency control mechanism and a recovery mechanism for our proposed methods. Simulation results are presented comparing the performance of our proposed methods and the conventional transaction processing method based on the two-phase commit protocol. The results demonstrate that the effective use of database migration produces better performance than the conventional method     

An architecture for adaptive multimedia content delivery

In this paper, we propose an architecture for multimedia content delivery considering Quality of Service (QoS), based on both the policy-based network and the best-effort network. The architecture consists of four fundamental elements: multimedia content model, application level QoS policy, QoS adaptation mechanism, and delivery mechanism. Applications based on current architecture loses their meaning by drastically degrading quality when network congestion occurs. Despite of this all-or-nothing architecture, applications based on our adaptive architecture can reduce its quality and then negotiate with the network entity, keeping its quality measure as much as possible even when network congestion occurs. We may consider a quality measure for Web pages, total page transmission time, and transmission order of inline objects as a segregation. We then define a language to specify application level QoS policies for Web pages and implement a delivery mechanism and a QoS adaptation mechanism to fulfill these policies. Kaname Harumoto, Ph.D.: He received the M.E. and Ph.D. (Eng.) degrees from Osaka University, Osaka, Japan, in 1994 and 1998, respectively. From 1994 through 1999, he was with the Department of Information Systems Engineering, Grauuate School of Engineering, Osaka University. Since November 1999, he has been an Assistant Professor in Computation Center (currently, the name has changed to Cybermedia Center), Osaka University. His research interests include database systems, especially in advanced network environments. He is a member of IEEE. Tadashi Nakano: He received the B.E. degree from Osaka University in 1999. Currently, he is a Ph.D. candidate in Graduate School of Engineering, Osaka University. His current reeearch interests include multimedia content delivery architecture. Shinji SHIMOJO, Ph.D.: He received the M.E. and a Dr.E. degrees from Osaka University in 1983 and 1986, respectively. From 1986 through 1989, he was an Assistant Professor in the Department of Information and Computer Sciences, Faculty of Engineering Science, Osaka University. From 1989 through 1998, he was an Associate Professor and since 1998, he has been a Professor in Computation Center (currently, the name has changed to Cybermedia Center), Osaka University. He was engaged in the project of object-oriented multimedia presentation system called Harmony. His current interests cover wide diversity of multimedia applications such as News On Demand System, multimedia database and networked virtual reality. He is a member of ACM and IEEE.     

Harmonic Analysis of Chopper Controlled Electric Rolling Stock

Chopper controlled electric rolling stock is maintenance free and can reduce power consumption considerably. Comfort and operating performance are both good. Because of these and other features, such rolling stock is now being widely used. However, there are several problems concerning this equipment, for example, harmonic current, its inductive interference, control system, etc. Therefore careful investigations are needed to solve these problems. This paper deals with the harmonic problems which occurs in chopper controlled electric rolling stock in the case of chopper normal or abnormal operation.