Experimental study on severe plastic deformation of Ti by novel equal-channel angular pressing

This study involves experimental investigation on severe plastic deformation (SPD) of Ti using novel equal-channel angular pressing (ECAP) at ambient temperature. Ti wire is tightly encapsulated in a hollow host material made of Al-based functionally graded material (FGM). The host material is prepared by embedding Al–Al3Ti alloy into Al. Three types of the Al–Al3Ti alloys with different Al3Ti volume fractions are used to prepare the host materials. ECAP for specimens is carried out for up to eight passes by route A. The microstructure and hardness of ECAPed specimens are investigated. The changes in microstructure and the increase in the hardness value of Ti with increased number of ECAP passes are evidences showing that Ti is successfully deformed by this technique

Formation of compositional gradient in Al/SiC FGMs fabricated under huge centrifugal forces using solid-particle and mixed-powder methods

Formations of graded distribution of SiC ceramic particles within the hollow cylindrical shaped Al/SiC functionally graded materials (FGMs) fabricated by centrifugal solid-particle method (CSPM) and centrifugal mixedpowder method (CMPM) under huge centrifugal force are experimentally and theoretically investigated. The movement of SiC ceramic particles in viscous liquid under centrifugal force is explained based on Stoke's law. The effect of compositional gradient of particles on viscosity is taken into account. Also, the effect of temperature distribution on viscosity and density are considered. A computer code to simulate the formation of compositional gradient in the Al/SiC FGMs fabricated by CSPM and CMPM is developed. From the results, it is found that the volume fraction of SiC ceramic particles can be graded from the inner to the outer surface of hollow cylindrical shaped Al/SiC FGMs by CSPM. Meanwhile by CMPM, the SiC ceramic particles can be dispersed on the outer surface of hollow cylindrical shaped Al/SiC FGMs. The graded distribution in Al/SiC FGMs under huge centrifugal force is found to be significantly affected by the mold temperature but less affected by the temperature of molten Al and casting atmosphere

Finite element analysis of severe plastic deformation of difficult-to-work material by equal-channel angular pressing at ambient temperature

An alternative technique of the equal-channel angular pressing (ECAP) process for difficult-to-work materials at ambient temperature is proposed by embedding a difficult-to-work material into an easy-to-work material. The easy-to-work material as a host material assists the deformation of the difficult-to-work material. The ECAP process is simulated by the finite element method (FEM). For this study, Ti as the difficult-to-work material is embedded into an Al-based functionally graded material (FGM) matrix. FEM is conducted with Ti embedded into a different host material type as well as a different die channel geometry. The strain distribution of the specimen after a single ECAP pass is analyzed. From the obtained results, it is found that the strain distribution in Ti is strongly influenced by the host material and the shape of the die channe

New Processing Routes for Functionally Graded Materials and Structures through Combinations of Powder Metallurgy and Casting

New processing routes for metal-matrix functionally graded materials (FGMs) and structures through combinations of powder metallurgy and casting are described in this chapter. Centrifugal mixed-powder method is introduced as a processing method for metal-matrix FGMs at first. The centrifugal mixed-powder method is a developed technique of centrifugal casting by setting predesigned mixed powder in a spinning mold in advance. As an example of processed FGMs by this method in our previous studies, Cu-based FGMs with dispersed diamond particles are shown. Graded structures in the Cu-based FGMs are investigated through scanning electron microscope (SEM) observations of microstructures. As the latest processing method for metal-matrix FGMs developed by our research group, centrifugal sintered-casting method is shown. The centrifugal sintered-casting method is a modified processing technique of the centrifugal mixed-powder method. In the centrifugal sintered-casting method, FGMs are processed by the combination of centrifugal sintering and centrifugal casting. Al–Si alloy and Cu-based FGMs with dispersed diamond particles are introduced as examples. Applications of metal-matrix FGMs processed by the centrifugal sintered-casting method are also described. Fabricated metal-matrix FGMs can be used as grinding wheel and applied to carbon fiber-reinforced plastic (CFRP) machining

Coevolutionary genetic algorithm for constraint satisfaction with a genetic repair operator for effective schemata formation

We discuss a coevolutionary genetic algorithm for constraint satisfaction. Our basic idea is to explore effective genetic information in the population, i.e., schemata, and to exploit the genetic information in order to guide the population to better solutions. Our coevolutionary genetic algorithm (CGA) consists of two GA populations; the first GA, called “H-GA”, searches for the solutions in a given environment (problem), and the second GA, called “P-GA”, searches for effective genetic information involved in the H-GA, namely, good schemata. Thus, each individual in P-GA consists of alleles in H-GA or “don't care” symbol representing a schema in the H-GA. These GA populations separately evolve in each genetic space at different abstraction levels and affect with each other by two genetic operators: “superposition” and “transcription”. We then applied our CGA to constraint satisfaction problems (CSPs) incorporating a new stochastic “repair” operator for P-GA to raise the consistency of schemata with the (local) constraint conditions in CSPs. We carried out two experiments: First, we examined the performance of CGA on various “general” CSPs that are generated randomly for a wide variety of “density” and “tightness” of constraint conditions in the CSPs that are the basic measures of characterizing CSPs. Next, we examined “structured” CSPs involving latent “cluster” structures among the variables in the CSPs. For these experiments, computer simulations confirmed us the effectiveness of our CGA</p

Energy Homeostasis by the Peripheral Serotonergic System

Energy homeostasis is maintained by balancing energy intake and energy expenditure. In addition to the central nervous system, several hormones play a key role in energy homeostasis in the whole body. In particular, serotonin is regarded as one of the key regulators of energy homeostasis. Serotonin is unique in that it is able to act in both the brain as a neurotransmitter and the peripheral tissue as a gastrointestinal hormone. In the brain, serotonin is thought of as a pharmacological target for anti-obesity treatments because it greatly inhibits meal size and body weight gain. In contrast, serotonin in the periphery has not been targeted as a strategy for anti-obesity treatment, even though almost all of the serotonin produced in the body is produced in the peripheral tissue. Recently, the peripheral serotonergic signal has been shown to regulate glucose and lipid metabolism through autocrine and paracrine signals in energy homeostasis-related tissues, including the pancreatic ? cell, liver, white adipose tissue, brown adipose tissue, and skeletal muscle. Thus, it is possible that the serotonergic system in the peripheral tissue is a new therapeutic target for metabolic disease, including obesity and diabetes. Here, we summarize the role of peripheral serotonin in the regulation of energy homeostasispublishersversio

Bovine Myoblast Differentiation

Satellite cells are involved in postnatal myogenesis and in muscle hypertrophy. A better understanding of the mechanisms of myogenesis is useful to improve the muscle production in farm animals. Herein, we show the cytokine effects on the myogenesis in bovine myoblast cultures. Acidic fibroblast growth factors (aFGF) and interleukin 1 (IL-1) stimulated the cell proliferation, and insulin-1ike growth factor-I (IGF-I) stimulated to form multinucleated myotubes. Thus, it was possible to regulate the bovine myoblast differentiation by aFGF, IL-1 and/or IGF-I. Using the culture system, the expression of myosin heavy chain (MyHC) isoforms was detailed in bovine myoblasts during the differentiation. It was immunohistochemically confirmed that bovine myoblasts expressed β/slow-type MyHC (MyHC-slow), fast-type MyHC (MyHC-fast) and developmental-type MyHC (MyHC-dev) isoforms. Furthermore, the expression of fast 2a and β/slow MyHC mRNA was recognized in the cultures of bovine myoblasts. The results support the existence of bovine myoblast phenotypes that express differentially MyHC isoforms