Dynamic Transformation Mechanism for Producing Ultrafine Grained Steels

Ultrafine grained (UFG) steels with grain sizes around 1 micron exhibit an excellent strength‐ductility combination and have been extensively studied worldwide. Among the different grain refinement strategies, thermomechanical controlled processing (TMCP) employing dynamic transformation (DT), that is, ferrite transformation during deformation of austenite, is considered as the simplest and commercially exploitable approach to produce ultrafine ferrite (UFF) with grain size of a couple of microns or below. The present paper reviews the research history of DT and highlights the major aspects of continuous interest including the methods and evidences for identifying DT, thermodynamics and kinetics of DT, mechanism for UFF formation and the effects of some key thermomechanical parameters on DT (and UFF formation), together with an outlook for the future research, and new TMCP design for industrial application. This paper also discusses some areas remaining under debate such as the diffusional or displacive mechanism, thermodynamic modeling, and the mechanism for UFF formation, etc.

     

Numerical modeling of multiphase diffusion in the process of homogenizing in binary alloys

A general model to treat multiphase diffusion in an impregnated semi-infinite couple, a finite/semi-infinite couple, and a finite/finite couple, under conditions of zero zurface flux, is presented. The model is based both on the numerical solutions previously presented for the multiphase diffusion in semi-infinite and infinite media to which Boltzmann's transformation can be applied and on the finite difference solutions with a variable grid for the multiphase diffusion to which the transformation cannot be applied. Not only critical layer widths for the occurrence of a new phase and the disappearance of a pre-existing phase but also criteria to calculate or not a change in concentration for a terminal phase are introduced in the model in order to diminish the number of iterations, in the calculation. Typical examples to which the model has been applied are discussed.     

Numerical modeling of multiphase diffusion in the process of homogenizing in binary alloys

A general model to treat multiphase diffusion in an impregnated semi-infinite couple, a finite/semi-infinite couple, and a finite/finite couple, under conditions of zero surface flux, is presented. The model is based both on the numerical solutions previously presented for the multiphase diffusion in semi-infinite and infinite media to which Boltzmann’s transformation can be applied and on the finite difference solutions with a variable grid for the multiphase diffusion to which the transformation cannot be applied. Not only critical layer widths for the occurrence of a new phase and the disappearance of a pre-existing phase but also criteria to calculate or not a change in concentration for a terminal phase are introduced in the model in order to diminish the number of iterations in the calculation. Typical examples to which the model has been applied are discussed.     

Identification of characterization factor for power system oscillation based on multiple synchronized phasor measurements

Electric power systems in Japan are composed of remote and distributed location of generators and loads mainly concentrated in large‐demand areas. The structures having long‐distance transmission tend to produce heavy power flow with increasing electric power demand. In addition, some independent power producers (IPP) and power producer and suppliers (PPS) are participating in the power generation business, which makes power system dynamics more complex. However, there was little observation as a whole power system. In this paper the authors present a global monitoring system of power system dynamics by using the synchronized phasor measurement of demand‐side outlets. Phasor Measurement Units (PMU) are synchronized based on the global positioning system (GPS). The purpose of this paper is to show oscillation characteristics and methods for processing original data obtained from PMU after certain power system disturbances triggered by accidents. This analysis resulted in the observation of the lowest and the second lowest frequency mode. The derivation of eigenvalue with the two‐degree‐of‐freedom model brings a monitoring of two oscillation modes. Signal processing based on wavelet analysis and simulation studies to illustrate the obtained phenomena are presented in detail. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 10– 18, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20316     

Gene locus for autosomal recessive distal myopathy with rimmed vacuoles maps to chromosome 9

Distal myopathy with rimmed vacuoles is an autosomal recessive muscular disorder, characterized clinically by weakness of the distal muscles in the lower limbs in early adulthood. Recently, the gene locus for familial vacuolar myopathy with autosomal recessive inheritance (hereditary inclusion body myopathy) was mapped to chromosome 9 by genome-wide linkage analysis of nine Persian-Jewish families. Since both disease conditions share similar clinical, genetic, and histopathological features, we analyzed seven families with distal myopathy with rimmed vacuoles using ten microsatellite markers within the region of the hereditary inclusion body myopathy locus. Significantly high cumulative pairwise lod scores were obtained with three markers: D9S248 (Z(max) = 5.90 at theta = 0), D9S43 (Z(max) = 5.25 at theta = 0), and D9S50 (Z(max) = 4.23 at theta = 0). Detection of obligate recombination events as well as multipoint linkage analysis revealed that the most likely location of the distal myopathy with rimmed vacuoles gene is in a 23.3-cM interval defined by D9S319 and D9S276 on chromosome 9. The results raise the possibility that distal myopathy with rimmed vacuoles and hereditary inclusion body myopathy in Persian Jews are allelic diseases.     

Compact low-cross-polarization horn antennas with serpentine-shaped taper

A compact horn with low cross polarization component less than -35 dB over 5% frequency bandwidth has been obtained by optimizing the taper configuration. To reduce the gain loss caused by spherical wavefront in a short length horn with a large flare angle, a serpentine-shaped taper successfully generates five higher-order modes. Such a taper configuration is represented by varying lengths of various uniform waveguides in stepwise approximation, while keeping the dimension of each step discontinuity constant. As a result, the computational time for obtaining the proposed horn is greatly reduced because scattering matrices of the step discontinuities are pre-calculated before the optimization. The verification of its high performance has been performed numerically and experimentally.     

MD simulation of atom-order void formation in Ni fcc metal

Atom-order void formation in a defective crystalline material is studied by using molecular dynamics method (MD). Infinite long cylinder, which is constructed with nickel atoms with a line of vacancies, is subjected to multiaxial tensile strain field by moving periodic boundary and the atoms on the outer surface of the cylinder. When the load exceeds a critical value, sudden appearance of the void is observed and it develops rapidly. The developed void does not disappear by only unloading and relaxation, in spite of the system with the void has higher potential energy than that without void. The biaxial or the triaxial load is necessary to the atom order void formation. Moreover, the results by the MD simulations are compared with theoretical solution for nonlinear elastic solid. Received 26 August 1999     

Syntheses and antitumor activity of cis-restricted combretastatins: 5-membered heterocyclic analogues

A series of cis-restricted combretastatin analogues with 5-membered heterocycles were synthesized and their inhibitory activity against microtubule assembly and cytotoxic activity against the colon 26 adenocarcinoma cancer cell line were evaluated. Some of the heterocyclic analogues showed potent antitubulin activity and cytotoxicity. Compounds 16 and 35 showed marked tumor growth suppression in the colon 26 murine tumor model.     

Evaluation of the PyloriTek test for detection of Helicobacter pylori infection in cases with and without eradication therapy

OBJECTIVE: The accuracy of the PyloriTek test (a 1-h rapid urease test) used after eradication therapy of Helicobacter pylori (H. pylori) has not been well clarified. This study was done to evaluate the accuracy of the PyloriTek test results for cases with and without eradication therapy, using culture and histology as gold standard methods, and to establish the suitable timing of the PyloriTek test after eradication treatment. METHODS: One hundred sixty-three patients undergoing upper endoscopy were randomly selected; 100 patients had not received eradication therapy and 63 had. Three biopsy specimens each were obtained from the gastric antrum and the body for examination by PyloriTek, culture, and histology. The absence of H. pylori was established with negative results from both culture and histology. RESULTS: In cases without eradication therapy, PyloriTek, correctly identified 66 of 67 H. pylori-positive cases and 30 of 33 H. pylori-negative cases, yielding 98.5% sensitivity and 90.9% specificity. In cases with eradication therapy, PyloriTek gave correct diagnoses in 10 of 17 H. pylori-positive cases and in 45 of 46 H. pylori-negative cases, for 58.8% sensitivity and 97.8% specificity. However, when PyloriTek was used more than 4 months after the end of eradication therapy, both the sensitivity and the specificity increased to 100%. CONCLUSION: Considering time and cost, the use of PyloriTek alone may be satisfactory for detecting H. pylori infection in cases without eradication therapy. When patients are examined more than 4 months after intervention, the use of PyloriTek alone may be sufficient for correctly diagnosing H. pylori infections.     

A 16-Mb Toggle MRAM With Burst Modes

This paper describes a recently developed 16-Mb toggle magnetic random access memory (MRAM). It has 100-MHz burst modes that are compatible with a pseudo-SRAM even though the toggle cell requires reading and comparing sequences in write modes. To accelerate operating clock frequency, we propose a distributed-driver wide-swing current-mirror scheme, an interleaved and pipelined memory-array group activation scheme, and a noise-insulation switch scheme. These circuit schemes compensate the toggle cell timing overhead in write modes and maintain write-current precision that is essential for the wide operational margin of MRAMs. Because toggle cells are very resistant to write disturbance errors, we designed the 16-Mb MRAM to include a toggle MRAM cell. The MRAM was fabricated with 0.13-mum CMOS and 0.24-mum MRAM processes with five metal layers.