Measurements of coupling and reflection characteristics of butt-joints in passive waveguide integrated laser diodes

Amplified spontaneous emission (ASE) spectra of passive waveguide integrated lasers have been studied to estimate the coupling efficiency and the reflectivity at the butt-joints between active and passive waveguides. A new method has been proposed for the analysis of ASE to extract the coupling efficiency and reflectivity at the butt-joints. This method was applied experimentally to estimate the coupling and reflection of the passive waveguide integrated lasers with different amounts of vertical misalignments of active and passive waveguides.     

Structural system identification: from reality to models

The paper is an expository contribution on the subject of structural system identification, measured signal processing and their applications to model-based structural health detection. The materials covered in this paper are by and large extracted from the three theses of the first three authors. The paper focuses on the state-space oriented system identification theory as specialized to structural dynamics governing equations of motion, a judicious use of wavelet transformation techniques for extracting impulse response functions, various input-output combinations for multi-input and multi-output problems, robust ways of identifying both proportional and non-proportional damping parameters, and the use of localized identification theory for damage detection from measured response data. The authors then offer several outstanding challenges in structural system identification theory and their applications.     

Hierarchically Ordered Polymer Films by Templated Organization of Aqueous Droplets

Hierarchically ordered structures facilitate the incorporation of diverse functions simultaneously. The present report introduces a simple and novel strategy for producing hierarchically ordered polymeric films. Hierarchical ordering of aqueous droplets on a polymer solution is realized by the imposition of physical confinement via various shaped gratings. After drying of the solution, well‐ordered hierarchical structures were fabricated in the remaining polymer film. The size of the grating structure and the lattice size of spontaneous hexagonally packed aqueous pores comprise two different length scales, thereby offering multiscale ordering. Interfacial wetting of the polymer solution to the grating surface was crucial in terms of obtaining a highly ordered structure that can be tuned by dissolving a small amount of surfactant in the polymer solution. The present novel approach provides a new opportunity for lithography‐free fabrication of complex hierarchical structures.     

540kN力基准机砝码摆动的研究

日本国家计量研究院(National Research Laboratory of Metrology)540kN静重式力基准机中的振荡分量主要是由于砝码的摆动引起的。本文对砝码的动态特性做了详细的分析，给出了其摆动的轨迹图，并对由于砝码摆动引起的相对不确定度进行了评估。提出了一类采用传感器并联的叠加系统(以下称叠加系统)输出的力值信号来评估砝码动态特性的信号处理方法。它对研究静重式测力机砝码摆动提供了有效的分析方法。     

Epitaxial growth of GaN on (0001) Al<Subscript>2</Subscript>O<Subscript>3</Subscript> via solution-cast seed layer formation process using Ga(mDTC)<Subscript>3</Subscript>

This paper reports an alternative method for the growth of GaN epitaxial layer on (0001) Al₂O₃ substrate by hot-wall vapor phase epitaxy technique. Tris (N,N-dimethyldithiocarbamato)-gallium (III), Ga(mDTC)₃ was introduced as a precursor material for the seed layer formation in the growth of GaN. Optimal growth conditions with seed layers formed by the Ga(mDTC)₃ concentration of 0.047 mol/L were identified: Growth temperature was found to be 850 °C, and optimal distance between the reactant outlet and substrate was determined to be 12.5 cm. Characterization results showed that this growth method produce high-crystallinity GaN epitaxial layers at a relatively lower growth temperature compared to the existing growth techniques and simplify the growth process.     

Nucleoside-diphosphate kinase-mediated signal transduction via histidyl-aspartyl phosphorelay systems in Escherichia coli

Nucleoside-diphosphate kinase (NDP kinase), a key enzyme in nucleotide metabolism, is also known to be involved in growth and developmental control and tumor metastasis suppression. Interestingly, we find that coexpression of NDP kinase with Taz1, a Tar/EnvZ chimera, in the absence of its native signal, can activate a porin gene ompC-lacZ expression in Escherichia coli. Further studies show that NDP kinase can act as a protein kinase to phosphorylate histidine protein kinases such as EnvZ and CheA which are members of the His-Asp phosphorelay signal transduction systems in E. coli. Instead of ATP, the exclusive phosphodonor for histidine kinases, GTP can be utilized in vitro in the presence of NDP kinase to phosphorylate EnvZ and CheA, which then transfer the phosphoryl group to OmpR and CheY, the respective response regulators. The direct involvement of GTP for the phosphorylation of EnvZ through NDP kinase was further demonstrated by the use of a mutant EnvZ, which lost ability to be autophosphorylated with ATP. Phospho-OmpR thus formed can bind specifically to an ompF promoter sequence. These results suggest that NDP kinase may play a physiological role in signal transduction.     

Discrete-time adaptive sliding mode power system stabilizer with only input/output measurements

In this paper a discrete-time adaptive sliding mode control method is newly developed and applied to the power system stabilization problem. A controllable canonical form of state space realization is constructed using the parameters identified by the on-line recursive least squares method and the system state is estimated from the input/output measurements and the simple state transformations. The identified parameters and the estimated state are then used by the discrete-time sliding mode control, which is suitable for the digital equipment. The most important advantage of the proposed power system stabilizer (PSS) is that it is able to maintain its regulating performance with a slower sampling period than that of the conventional sliding mode PSS because it is developed in a pure discrete-time domain. Another advantage of the proposed PSS is that it needs neither a mathematical model of the power system nor the full-state measurements because they are identified through on-line identifications. Several computer simulations for the linear power system are performed to verify the performance of the proposed PSS. In the computer simulations for various circumstances which are probable in a power system are considered, such as transitions of the active and reactive powers, change of parameters of the synchronous machine, line-to-ground faults and measurement noise. As a result, a new power system stabilizer which can operate in a wide range of operating conditions and can overcome various disturbances and measurement noises is proposed.     

Nicalon-fibre-reinforced silicon-carbide composites via polymer solution infiltration and chemical vapour infiltration

A new, faster process was developed for the fabrication of Nicalon-fibre-reinforced SiC composites by combining polymer solution infiltration (PSI) and chemical vapour infiltration (CVI). The process led to the near-net-shape fabrication of fibre-reinforced ceramic-matrix composites and reduced infiltration time. Typical flexural strength and fracture toughness of these composites were 296 MPa and 10.9 MPa m^1/2 at room temperature (RT) and 252 MPa and 9.6 MPa m^1/2 at 1000 °C, respectively. The composites exhibited load-carrying capability after crack initiation.     

Performance of GaAs-AlGaAs V-grooved inner stripe quantum-well wirelasers with different current blocking configurations

GaAs-AlGaAs V-grooved inner stripe (VIS) quantum-well wire (QWW) lasers grown by metalorganic chemical vapor deposition with different current blocking configurations, n-blocking on p-substrate (VIPS), p-n-p-n blocking on n-substrate (VI(PN)_nS) and p-blocking on n-substrate (VINS) have been fabricated and characterized. The VIPS QWW lasers show the most stable characteristics with effective current confinement: one of the lasers shows fundamental transverse mode, lasing up to 5 mW/facet, typical threshold current of 39.9 mA at 818.5 mm, an external differential quantum efficiency of 24%/facet, and characteristic temperature of 92 K. The current tuning rate was almost linear at 0.031 mm/mA, and the temperature tuning rate was measured to be 0.14 nm/°C. Comparison of the light output versus current characteristics of the lasers with different current blocking configurations is presented here