Stochastic theory of minimal realization

In this paper it is shown that a natural representation of a state space is given by the predictor space, the linear space spanned by the predictors when the system is driven by a Gaussian white noise input with unit covariance matrix. A minimal realization corresponds to a selection of a basis of this predictor space. Based on this interpretation, a unifying view of hitherto proposed algorithmically defined minimal realizations is developed. A natural minimal partial realization is also obtained with the aid of this interpretation.     

Bending fracture rule for 3D-printed curved continuous-fiber composite

Three-dimensional (3D) printing is an attractive technology to produce complex structures without the need for expensive tools and molds. Additives are usually incorporated with the plastic materials used in 3D printing to increase their strength and rigidity. In particular, carbon fiber-reinforced plastic (CFRP) shows promise as a material for use in 3D printing. However, the strength of CFRP after printing is still unclear, although it is known that its strength is affected by the plastic melting during printing. In this study, we analyzed the fracture behavior of CFRP specimens before and after bending to different curvature radii. From the experimental results, a fracture criterion that described the behavior of the materials by considering tensile and compressive loads was developed. The fracture mechanism was the same for CFRP specimens with different curvature radii. These results increase our understanding of the mechanical properties of CFRP materials used in 3D printing.     

GFP expression by intracellular gene delivery of GFP-coding fragments using nanocrystal quantum dots

Gene therapy is an attractive approach to supplement a deficient gene function. Although there has been some success with specific gene delivery using various methods including viral vectors and liposomes, most of these methods have a limited efficiency or also carry a risk for oncogenesis. We herein report that quantum dots (QDs) conjugated with nuclear localizing signal peptides (NLSP) successfully introduced gene-fragments with promoter elements, which promoted the expression of the enhanced green fluorescent protein (eGFP) gene in mammalian cells. The expression of eGFP protein was observed when the QD/gene-construct was added to the culture media. The gene-expression efficiency varied depending on multiple factors around QDs, such as (1) the reading direction of the gene-fragments, (2) the quantity of gene-fragments attached on the surface of the QD-constructs, (3) the surface electronic charges varied according to the structure of the QD/gene-constructs, and (4) the particle size of QD/gene complex varied according to the structure and amounts of gene-fragments. Using this QD/gene-construct system, eGFP protein could be detected 28 days after the gene-introduction whereas the fluorescence of QDs had disappeared. This system therefore provides another method for the intracellular delivery of gene-fragments without using either viral vectors or specific liposomes.     

A Low‐Loss Medium‐Voltage Inverter Applying Series Connected General Purpose 1.2 kV Insulated Gate Bipolar Transistors with Accurate Voltage Balancing Techniques

This paper presents a medium‐voltage inverter applying series connected general‐purpose 1.2 kV insulated gate bipolar transistors (IGBTs) as a switching device to achieve low switching losses compared to inverters applying high‐voltage IGBTs with over 3 kV rating. Gate signal synchronization, which is essential to keep the balance of collector‐emitter voltages across the IGBTs, is achieved by magnetically coupling all gate lines using a simple two‐windings transformer. In order to obtain better voltage balancing, influence of stray capacitance distribution associated with an insulating substrate in a two‐in‐one IGBT module on the voltage sharing is investigated, and an optimized layout of heat sinks for the IGBT modules is proposed. To validate some performances concerning the device losses and the voltage sharing, a 170 kVA inverter based on three 1.2 kV IGBTs connected in series is built and evaluated. The experimental results are shown. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An improved method of voltage utility factor for PWM control of a five‐leg inverter in two induction motor drives

This paper presents an improved method of voltage utility factor (VUF) from 50 to 86.6% for a five‐leg inverter when two induction motors are driven in vector control and in a condition where the frequencies of the two motors are not very different, and the improved method of voltage utility is theoretically shown. Many modulation methods for the five‐leg inverter have been proposed, but the voltage utility factor is 50% in these methods. The voltage utility factor of the five‐leg inverter is lower than that of the three‐leg inverter as maximum voltage utility factor of the three‐leg inverter is 100%. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

On the linearity and efficiency of outphasing microwave amplifiers

A new approach for the analysis of the efficiency and linearity of Chireix-outphasing combiners is presented. The approach takes into account, in an explicit manner, the effect of impedance mismatch between the amplifiers and the lossless combining structure. It is shown that the impedance mismatch leads to new expressions for the output voltages from both branches of the amplifier. These expressions explain the origin of the lack of linearity reported in the literature for the Chireix architecture and lead to a new expression for the instantaneous efficiency of a Chireix combiner. Various simulations using a commercial simulator are performed and their results are compared to those predicted by the derived equations. A quasi-exact agreement between the simulator and derived equations is found for all simulations conducted, including voltage expressions, linearity analysis, and instantaneous and average efficiency calculations for a code-division multiple-access signal. The impact of combiner parameters on its linearity and efficiency is also studied.     

Hydrothermal treatment of glycine and adiabatic expansion cooling: implications for prebiotic synthesis of biopolymers

There have been several studies on biopolymer synthesis under hydrothermal conditions. The conventional hydrothermal methods make it possible to synthesize only a dipeptide and short oligopeptides as well as cyclo-dimer, from amino acids. As these studies that were applied with various quenching methods suggested the importance of quenching rate from hydrothermal conditions, rapid quenching could avoid hydrolysis of the oligomers that had already been synthesized under hydrothermal conditions. In this study, therefore, we designed a novel hydrothermal flow reactor adopted with adiabatic expansion cooling system from the reason that it was thought to be one of the most rapid quenching methods. It mimics geysers, fumaroles, hot springs, and volcanic eruptions. Once aqueous solutions of monomers were treated at high temperature and pressure, the solutions were released into the atmosphere through an orifice to be depressurized and cooled down simultaneously with the Joule–Thomson effect. We demonstrated oligomerization of glycine up to decamer (Gly₁₀) by using the flow reactor, which had never been yielded with any other quenching methods. This suggests that rapid quenching methods under non-equilibrium conditions such as adiabatic expansion cooling is an efficient way to produce long oligomers connected by covalent bonds via dehydration condensation.     

Sensorless Vector Control of Parallel-Connected Multiple Induction Motors Fed by a Single Inverter

KoukiMatsuse:Sensorlessvectorcontrolofparallel connectedmultipleinductionmotorsFedbyasingleinverter　　　InEq.(12) Φerand iesaredividedintode qeaxiscomponent,thenEq.(12)isexpressedby: T′=p M′{ ieqsedr- iedseqr Δ ieqsΔeqr-Δ iedsΔeqr}(17)