A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.     

Polarity control of GaN epilayers grown on ZnO templates

We report the successful growth of Ga-polar GaN epilayers on O-polar ZnO templates pre-deposited on c-sapphire. Prior to GaN growth, NH₃ is exposed onto the ZnO template. The polarity of the GaN layers is confirmed by etching of the surface and by conversion beam electron diffraction (CBED), while the O-polar ZnO is confirmed by CBED. It is suggested that the NH₃ pre-exposure helps form a Zn₃N₂ layer, which possesses inversion symmetry and inverts the crystal from anion polar to cation polar.     

Thermodynamic modeling of the Au-In-Sb ternary system

The phase diagram of the Au-In-Sb ternary system is of importance in predicting the interface reaction between In-based solders and the Au substrate. Using the calculated phase diagram method and based on experimental data of thermodynamic properties and phase boundaries, the Au-Sb binary system was assessed, and the In-Sb binary system was revised. On the basis of the constituent binary systems, Au-Sb, In-Sb, and Au-In, the Au-In-Sb ternary system was modeled. Several isothermal and vertical sections were calculated, among which the one at 500 K reproduces the experimental diagram well.     

日本移动服务业的过去和将来

分别对日本三代移动通信系统的发展进行了描述。第一代系统致力于实现随时、随地的通话，第二代系统的特征是基于语音的附加服务、低速的移动计算、移动因特网和位置服务，第三代系统将以基于视频的全球范围内高速多媒体服务和移动IT为特征。在未来的后3G系统中，这些服务都将以虚拟永远在线的方式无缝、高速地普遍提供。     

DC voltage control strategy for a five-level converter

This paper describes a control method for a three-phase five-level diode-clamp pulse width modulation (PWM) converter considering DC-link capacitor voltage balancing problem. The proposed control circuit uses multiband hysteresis comparators (MHCs) to simplify the control of the main circuit. The DC-link capacitor voltage balancing problem is solved by changing the shape of the MHC. The proposed method can (1) overcome voltage imbalance at the DC-link capacitors; (2) achieve a unity power factor; (3) generate nearly sinusoidal input currents; and (4) regenerate electric power back to the power system. Simulation and experimental results demonstrate the validity of the proposed method     

Preparation of CdSSe-ZnS superlattice,SrS, and CdSSe-SrS superlattice by hot-wall epitaxy,and applications to electroluminescent devices

CdSSe (manganese-doped, E_g = 1.9–2.5 eV, lattice constant a = 6.05–5.8A)-ZnS (Eg = 3.56 eV, a = 5.41A) superlattices, SrS (cerium-doped, E = 4.4 eV, a = 6.02A) layers, and CdSSe-SrS (cerium-doped) superlattice layers nave been prepared by hot-wall epitaxy, and the properties and the electroluminescent device characteristics of the active layers are reported. For the superlattices with ZnS, the maximum luminance was 800 cd/m² at an applied sinusoidal voltage (V_o-p = 200 V) with frequency 1kHz, and the wavelength of the spectral peak was 610 nm due to the large strain caused by the lattice mismatch (8–15%) between the CdSSe and ZnS layers. The maximum luminance and Comisson Internationale de Enluminure (CIE) chromaticity of CdS(Mn)-ZnS superlattices and CdSe(Mn)-ZnS superlattice devices were 557cd/m² and (x,y) = (0.58,0.41) and 982 cd/m² and (0.61, 0.38), respectively. For superlattices with SrS, the maximum luminance of the device with the SrS (cerium-doped) active layer was nearly 700 cd/m² at a voltage of 340V. Blue electroluminescent emission was observed in the photon wavelength region less than 450 nm, due to carriers dropping into the quantum wells of the device with the CdSSe-SrS superlattice active layer.     

Large nonlinear optical effect in an InGaAs/InAlAs multiquantum well waveguide

All-optical refractive nonlinearity in a passive InGaAs/InAlAs multiquantum well waveguide is evaluated for TE and TM modes at 1.55 mu m wavelength and room temperature. A quarter wavelength change in the optical path length is observed at an input pump light power of 6.5 mW for 1.47 mu m wavelength in a 960 mu m long device. Nonlinear refractive index n/sub 2/ is evaluated to be -1.2*10/sup 6/ and -0.5*10-6cm/sup 2//W for the TE and the TM modes, respectively.<>     

Detection and Quantitation of Left-to-Right Shunts from Radionuclide Angiocardiography Using the Homomorphic Deconvolution Technique

The homomorphic filtering method is described for the detection and quantitation of left-to-right shunts from radionuclide angiocardiography. First, the method is investigated theoreticatly and numerically using a realistic model with systemic recirculation. It is demonstrated that even in a noisy situation the shunt flow fraction can be relatively well estimated, if only the characteristics of the fiters used are suitable. Second, the method is applied to real data, i.e., the pulmonary time-activity curves from radionucUde anglocardiography. The presence or absence of a left-to-right shunt is determined using the ratio AT/MTT. The pulmonary-to-systemic flow ratios calculated from the areas of the two decomposed curves are compared with those from oximetry at cardiac catheterization. Good agreement between the Qp/Qs ratios calculated by oximetry and radionucUide angiocardiography is obtained.     

Fermentation Process and Grain Structure of Baked Breads from Frozen Dough Using Freeze-Tolerant Yeasts

The fermentation process for frozen doughs using freeze‐sensitive (Saccharomyces cerevisiae, Kyowa for sweet bread; S. cerevisiae, FC for white bread) and freeze‐tolerant (S. cerevisiae, YF for sweet bread) yeasts was traced by magnetic resonance imaging (MRI). Grain network structures of baked breads were also visualized by MRI. Prefermentation before freezing, punching and remolding, or resheeting and molding treatments increased loaf volume by 10 to 110% for the baked breads using freeze‐tolerant yeast, while these treatments decreased loaf volume by 70% using freeze‐sensitive yeast. The first fermentation before freezing and the second fermentation with punching or resheeting after thawing are useful for obtaining good quality breads from frozen dough using freeze‐tolerant yeast.