1,722,221 research outputs found
Two-band excitation for HMM-based speech synthesis
No full textThis letter describes a two-band excitation model for HMM-based speech synthesis. The HMM-based speech synthesis system generates speech from the HMM training data of the spectral and excitation parameters. Synthesized speech has a typical quality of "vocoded sound" mostly because of the simple excitation model with the voiced/unvoiced selection. In this letter, two-band excitation based on the harmonic plus noise speech model is proposed for generating the mixed excitation source. With this model, we can generate the mixed excitation more accurately and reduce the memory for the trained excitation data as well
Grain size dependence of ductile-to-brittle transition temperature of a high-nitrogen Cr–Mn austenitic steel
No full textWith decreasing grain size, the yield and tensile strengths increased without a loss in ductility and the upper-shelf energy was also improved. However, the reduction of grain size had no beneficial influence on lowering the ductile-to-brittle transition temperature because it promoted the increase of yield stress with decreasing temperature. (C) 2011 Elsevier B.V. All rights reserved.X1110Nsciescopu
Medium Mn transformation-induced plasticity steels: Recent progress and challenges
No full text114224sciescopu
Effect of delta ferrite on impact property of hot-rolled 12Cr-Ni steel
No full textThe effect of delta ferrite (delta) on impact property of the 12Cr-Ni steel has been studied to some degree, but controversial literatures still exist. In order to clarify the effect of delta ferrite on toughness, volume fraction, the morphology and the degree of banding were taken into consideration. Three kinds of the 12Cr-Ni steels with slightly different chemical compositions were prepared in order to change the volume fraction of delta ferrite (delta). It was seen that toughness and the microhardness of martensite increase with increasing delta ferrite volume fraction, while the Brinell hardness decreases. The microhardness of delta ferrite seems to be little changed. The cleavage fracture area decreased with increasing test temperature and delta ferrite volume fraction. Charpy V-notch fracture toughness transition curves of the steels were determined. The impact energy of as-rolled plates increased, as the microstructural banding index decreased. From the 3D morphology of the delta ferrite (delta), possible effect of connections between bands was discussed. (C) 2013 Elsevier B.V. All rights reserved.X1157sciescopu
Elastic-plastic constitutive model for accurate springback prediction in hot press sheet forming
No full textThe present study investigates the effect of phase transformation plasticity on the springback of hot press formed parts. Employing an implicit finite element formulation to take phase transformations during rapid cooling from fully austenitic phase and their related thermo-mechanical behavior into account, two validations - (1) the loaded dilatometry problem which induces significant plastic deformation even at lower stress levels than the classical yield stress, and (2) the 2-D draw bending problem, which introduces high temperature forming and subsequent quenching - are presented and compared with known experimental data. The study showed that the magnitude of springback predicted by considering the phase transformation plasticity and the temperature change induced volumetric strain agreed well with date from experiments, while the results determined with the conventional elastic-plasticity theory in which only plastic deformation by external load was used, had considerable deviation for the springback profile after hot press forming. The negligible springback amount after hot press forming, which has been frequently reported in many experimental observations, is due to the stress relaxation by the addition of abnormal transformation plasticity.X111110sciescopuskc
Influence of production methods on creep deformation of cold rolled 329LA lean duplex stainless steel in continuous annealing condition
No full textThe effects of processing methods, line tension, cold reduction and temperature on creep deformation of 329LA lean duplex stainless steel under continuous annealing condition are investigated. Two different processes, conventional continuous casting followed by hot rolling process and strip casting process, were used to make steel plates. Creep tests were carried out at 1010 degrees C up to 1100 degrees C using cold rolled specimens with various cold reductions for both kinds of specimen. It was found that continuous cast specimens show higher strain rate than strip cast specimens when tested with the same cold reduction and stress condition at all temperatures. Creep strain rate increases with the increase of line tension, temperature and the amount of cold reduction. The measured strain rate sensitivity values (m), around 0.5, show the superplastic behavior of both continuous and strip cast specimens at all test conditions, while the stress exponents (n), around 2, are consistent with the model of grain/phase boundary sliding as the rate controlling mechanism. The strip cast specimen has a very inhomogeneous microstructure which leads to larger average grain size, while the continuous cast specimen shows a uniform distribution of ferrite (delta) and austenite (gamma). Electron back scattered diffraction (EBSD) results show that cold rolled texture is destroyed during heating to deformation temperature and delta/gamma interface becomes high angle boundary which slides easily. Lastly, phase boundary sliding during creep deformation was confirmed by scanning transmission electron microscopy (STEM) in both specimens. (C) 2015 Elsevier B.V. All rights reserved.111sciescopu
Busy period analysis for the GI/M/1 queue with exponential vacations
No full textWe consider the busy period in the GI/M/1 queue with multiple exponential vacations. We derive the transform of the joint distribution of the length of a busy period, the number of customers served during the busy period, and the residual interarrival time at the instant the busy period ends. (c) 2006 Elsevier B.V. All rights reserved.Korean Research Foundation Grant
(KRF-2004-015-C00084
Intergranular Cracking Susceptibility of 2.25Cr Heat-Resistant Steels Depending on Alloying Elements and Impurities
No full textThe intergranular cracking susceptibility of 2.25Cr heat-resistant steels increases with increasing bulk phosphorus content. This is due to the increase in phosphorus segregation concentration of prior austenite grain boundaries (PAGBs) and the prior austenite grain boundary/carbide interfaces (GCIs) with increasing bulk phosphorus content. Moreover, the susceptibility is higher in tungsten-added steels than the molybdenum-added steel. This is attributed to the higher driving force for carbide formation of tungsten which causes more active carbide formation in the tungsten-added steel, the consequent absence of the repulsive segregation between carbon and phosphorus, and the final higher phosphorus segregation concentration at the PAGBs and the GCIs. Additionally, the absence of sulfur segregation at the PAGBs and the GCIs of the molybdenum-added steel, which arises from the repulsive segregation between carbon and sulfur, acts as an additional factor which lowers the intergranular cracking susceptibility. (C) The Minerals, Metals & Materials Society and ASM International 20161153sciescopu
PARALLEL GENETIC ALGORITHMS FOR THE EARLINESS TARDINESS JOB SCHEDULING PROBLEM WITH GENERAL PENALTY WEIGHTS
No full textThe purpose of this paper is to develop parallel genetic algorithms for a job scheduling problem on a single machine. The objective of the scheduling is to minimize the total generally weighted earliness and tardiness penalties from a common due date. A binary representation scheme is employed for coding job schedules into chromosomes. Parallel subpopulations are constructed by considering only jobs that can be processed first in the schedule. Three important genetic algorithm operators; reproduction, crossover and mutation are implemented by reflecting the problem-specific properties. The efficiency of the parallel genetic algorithm is illustrated with computational results
Diagnosis of sensor faults in active magnetic bearing system equipped with built-in force transducers
No full textIn this paper, an on-line diagnosis scheme for sensor faults in an active magnetic bearing system equipped with builtin force transducers is proposed. The scheme, utilizing redundant signals, i.e., displacement, current, and force, is based on the causality between faults and symptoms. The main advantage of the scheme is that it is simple and efficient, because monitoring the symptom only is enough to diagnose a sensor fault with no elaborate signal processing. Experiments were also performed to demonstrate the effectiveness of the proposed method in the detection and diagnosis of sensor faults
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