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41.
We have investigated Pb(Zr,Ti)O3 (PZT) film composition suitable for highly reliable ferroelectric RAM (FeRAM) application. To obtain a wide operational margin for 2T/2C (two transistors and two capacitors) FeRAMs, the PZT film capacitor is needed to have a low coercive voltage (Vc) and a high dielectric constant on the polarization switching (ϵS) and a low dielectric constant on the nonswitching (ϵN), or essentially a large ϵS/ϵN ratio. Concerning the B-site composition in the perovskite structure, it is found that lowering the Zr/Ti ratio from 47/53 to Ti-richer ones increases the ratio of ϵS/ϵN as a positive effect on the wide operational margin, but increased Vc as a negative effect. Taking the balance of these factors into consideration, it is concluded that an optimum composition, such as Zr/Ti=30/70, provides the maximum operational margin. The A-site composition, on the other hand, affects the long-term reliability of a PZT capacitor. The endurance to the fatigue and imprint are enhanced by reduction of the Pb-excess and dope of La in the A-site. A La-doped PZT (Zr/Ti =30/70) capacitor is successfully integrated to the 8 kbit FeRAM macro with double-layer Al wiring to confirm the feasibility of this capacitor 相似文献
42.
General formulas for capacity of classical-quantum channels 总被引:2,自引:0,他引:2
Hayashi M. Nagaoka H. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(7):1753-1768
The capacity of a classical-quantum channel (or, in other words, the classical capacity of a quantum channel) is considered in the most general setting, where no structural assumptions such as the stationary memoryless property are made on a channel. A capacity formula as well as a characterization of the strong converse property is given just in parallel with the corresponding classical results of Verdu-Han (1994) which are based on the so-called information-spectrum method. The general results are applied to the stationary memoryless case with or without cost constraint on inputs, whereby a deep relation between the channel coding theory and the hypothesis testing for two quantum states is elucidated. 相似文献
43.
Matsumoto S. Hirabayashi K. Sakata S. Hayashi T. 《Photonics Technology Letters, IEEE》1999,11(4):442-444
An electrically tunable optical filter has been developed that uses a polymer containing fine droplets of nematic liquid crystal as the active cavity in a Fabry-Perot interferometer (FPI). This FPI filter, whose finesse was 62, had a free spectral range of 37 nm in the 1.55-μm range with a full-width at half maximum of 0.6 nm and a transmission loss of 2.4 dB. The polarization dependent loss was smaller than 0.17 dB. The transmitted peak wavelength decreased with an electric field. This resulted in a tuning range of 10 nm at 300 V. The switching time was about 370 μs 相似文献
44.
Shiga N. Nakajima S. Otobe K. Sekiguchi T. Kuwata N. Matsuzaki K.-i. Hayashi H. 《Microwave Theory and Techniques》1991,39(12):1987-1994
The design and test of an X -band monolithic four-stage low-noise amplifier (LNA) with 0.5 μm-gate pulse-doped GaAs MESFETs for application in a direct broadcast satellite (DBS) converter is presented. The key feature of the research is a detailed demonstration of the advantages of using series feedback with experiments and simulations. This LNA shows an excellent input VSWR match under 1.4 as well as a noise figure of 1.67 dB and a gain of 24 dB at 12 GHz. The noise figure, the gain and VSWRs exhibit very little bias current dependence due to the exceptional features of the pulse-doped structure FETs and the optimized circuit design. Insensitivity to bias current implies performance stability in the face of process fluctuations. Thus, the yield of chips with noise figures of less than 2.0 dB is as high as 62.5%, and the variations of gain and VSWR are highly uniform as well 相似文献
45.
Hiroyama R. Nomura Y. Furusawa K. Okamoto S. Hayashi N. Shono M. Sawada M. 《Electronics letters》2001,37(1):30-31
A record light output power of 240 mW has been achieved for the 780 nm band AlGaAs laser diodes by using a rectangular ridge structure. The laser diodes have been operated for >1000 h at 60°C under 150 mW pulsed operation 相似文献
46.
Wang Y Lui LM Gu X Hayashi KM Chan TF Toga AW Thompson PM Yau ST 《IEEE transactions on medical imaging》2007,26(6):853-865
In medical imaging, parameterized 3-D surface models are useful for anatomical modeling and visualization, statistical comparisons of anatomy, and surface-based registration and signal processing. Here we introduce a parameterization method based on Riemann surface structure, which uses a special curvilinear net structure (conformal net) to partition the surface into a set of patches that can each be conformally mapped to a parallelogram. The resulting surface subdivision and the parameterizations of the components are intrinsic and stable (their solutions tend to be smooth functions and the boundary conditions of the Dirichlet problem can be enforced). Conformal parameterization also helps transform partial differential equations (PDEs) that may be defined on 3-D brain surface manifolds to modified PDEs on a two-dimensional parameter domain. Since the Jacobian matrix of a conformal parameterization is diagonal, the modified PDE on the parameter domain is readily solved. To illustrate our techniques, we computed parameterizations for several types of anatomical surfaces in 3-D magnetic resonance imaging scans of the brain, including the cerebral cortex, hippocampi, and lateral ventricles. For surfaces that are topologically homeomorphic to each other and have similar geometrical structures, we show that the parameterization results are consistent and the subdivided surfaces can be matched to each other. Finally, we present an automatic sulcal landmark location algorithm by solving PDEs on cortical surfaces. The landmark detection results are used as constraints for building conformal maps between surfaces that also match explicitly defined landmarks. 相似文献
47.
Shinsuke Kajioka Naoki Wakamiya Hiroki Satoh Kazuya Monden Masato Hayashi Susumu Matsui Masayuki Murata 《Ad hoc Networks》2011,9(5):911-927
To accommodate real-time multimedia application while satisfying application QoS requirements in a wireless ad-hoc network, we need QoS control mechanisms. In this paper, we propose a new routing mechanism to support real-time multimedia communication by efficiently utilize the limited wireless network capacity. Our mechanism considers a wireless ad-hoc network composed of nodes equipped with multiple network interfaces to each of which a different wireless channel can be assigned. By embedding information about channel usage in control messages of OLSRv2, each node obtains a view of topology and bandwidth information of the whole network. Based on the obtained information, a source node determines a logical path with the maximum available bandwidth to satisfy application QoS requirements. Through simulation experiments, we confirmed that our proposal effectively routed multimedia packets over a logical path avoiding congested links. As a result, the load on a network is well distributed and the network can accommodate more sessions than QOLSR. We also conducted practical experiments using wireless ad-hoc relay nodes with four network interfaces and verified the practicality of our proposal. 相似文献
48.
V. N. Manuilov T. Idehara M. Kamada T. Hayashi La Agusu T. Kanemaki K. Yatsui Wiehua Jiang 《Journal of Infrared, Millimeter and Terahertz Waves》2006,27(3):343-353
High power Large Orbit Gyrotron (LOG) [1] is now under development at FIR FU. First version of this device was recently manufactured and then assembled with power supply ETIGO-IV [2]. Results of preliminary tests of electron-optic system are presented. The conditions when stable flat form of current pulse realized are discussed. Analytical estimations of cathode-anode distance to achieve small influence of cathode plasma during high voltage (HV) pulse are performed. Two new electron gun versions with decreased influence of the cathode plasma on its impedance and pulse form are suggested and optimized. New optimal magnetic field distributions are found. First gun has quiasi-flat cathode configuration near the anode diaphragm and provides operating current about 60 A. Second one uses blade cathode with operating current about 30 A. Beam quality for both guns is suitable for LOG operation. 相似文献
49.
Nakamura T. Hayashi N. Fukuda H. Yokokawa S. 《Electromagnetic Compatibility, IEEE Transactions on》1995,37(3):317-325
The transmission and radiation characteristics at an acute bend of a transmission line are investigated analytically. First, in consideration of the strong coupling to the adjacent conductor, the current distributions are decomposed into even and odd modes. Applying the traveling-wave mode method to these modes, it is shown that transmission characteristics of the line with an acute bend can be easily obtained. The abrupt variation of the voltage near the bend is noted. Next, the discontinuities of the traveling wave currents are regarded as radiating sources and the radiation field from the bend in the transmission line is derived by the summation of fields created by each of the discontinuities. It is found that there exist the electric field component radiating strongly in the directions of propagation of the current and another electric field component radiating strongly into the intermediate direction. Finally, by comparing with the former method and experimental results, the validity of the method is confirmed 相似文献
50.
Durable write-once (WO) optical disk media have been demonstrated by using silver island films with a protection layer of fluorine-contained polymers. The reflectance of the silver island films is high at the wavelength of 800 nm and can be greatly lowered by laser irradiation, owing to the thermal deformation or the islands. Laser writing has been experimentally confirmed at almost the same line speed as that of compact discs (CDs). Therefore it is expected that a CD-compatible write-once optical disc can be realised 相似文献