Grain size effect on high-speed deformation of Hadfield steel

The influence of the microstructure on the tensile properties and fracture behavior of Hadfield steel at high strain rate were studied. Hadfield steel samples with different mean grain sizes and carbon phases were prepared by rolling at medium temperatures and subsequent annealing. A sample with an average grain size larger than 10 μm, and a small number of carbides shows ductility with local elongation (post uniform elongation) at a high-speed tensile deformation rate of 10³ s⁻¹. In addition, the fracture surface changes from brittle to ductile with increasing strain rate. In contrast, a fine-grained sample with carbides undergoes brittle fracture at any strain rate. The grain size dependence is discussed by considering the dynamic strain aging as well as the emission of dislocation from cracks. The accelerated diffusion of carbon due to grain refinement is considered as one of the important reason for brittle fracture in the fine-grained Hadfield steel.     

Coulomb blockade behaviors in individual Au nanoparticles as observed through noncontact atomic force spectroscopy at room temperature

Coulomb blockade behaviors in individual Au nanoparticles of 2 nm core diameter in double-barrier structures have been studied by means of noncontact atomic force spectroscopy (NC-AFS) at room temperature. The Au nanoparticles with a 1-decanethiol ligand were chemisorbed by 1,10-decanedithiol molecules of a mixed 1-octanethiol/1,10-decanedithiol self-assembled monolayer coated on a Au(111) surface; these particles were observed through NC-AFS. NC-AFS measurements of the cantilever frequency shift-sample voltage (Δf-V(S)) curves were sequentially conducted on three Au nanoparticles under the same experimental conditions; the Δf-V(S) curves were found to deviate from the parabolic (Δf(N)) curve in the cases where no extra charge existed on the Au core. The experimental Δf(CB)(=Δf-Δf(N)) and Δf(CB)/V curves agree well with the theoretical curves obtained using a golden-rule calculation and the same parabolic parameters. All the results, through NC-AFS, suggest Coulomb blockade behaviors in the Au nanoparticles at room temperature.     

New detergent mechanism using cellulase revealed by change in physicochemical properties of cellulose

Sebum in naturally soiled cotton undershirt and oleic acid in artificially soiled cotton cloth, which entered interfiber space in the interior of cotton fibers were easily removed by alkaline cellulase fromBacillus sp., but only with difficulty by commonly used detergent ingredients such as surfactant and protease. Adsorption isotherms and the rate of hydrolysis of alkaline cellulase against insoluble cellulose powders revealed that the lower the relative crystallinity of cellulose powder, the more adsorptive alkaline cellulase became and the more hydrolysis was promoted. With alkaline cellulase, cotton having the highest relative crystallinity was adsorbed at pH 9 and 5°C, liberated a negligible small amount of reducing sugar at pH 9 and 40°C, and produced no changes in the degree of polymerization of cotton cellulose and in the tensile strength of cotton fabric at pH 9 and 30°C. On the other hand, differential scanning calorimetric studies revealed that under similar conditions even a small quantity of alkaline cellulase drastically reduced the amount of water bound to cellulose in cotton. Because water was bound only with hydroxy groups of cellulose molecules in the amorphous region of cotton fibers, it can be understood that soil entering the interfiber space of amorphous interlamellae in the interior of cotton fibers, was easily removed as the hydrated cellulose in the interlamellae was slightly hydrolyzed by alkaline cellulase. A new detergent mechanism is proposed.     

Transparent surface modeling from a pair of polarization images

We propose a method for measuring surface shapes of transparent objects by using a polarizing filter. Generally, the light reflected from an object is partially polarized. The degree of polarization depends upon the incident angle, which, in turn, depends upon the surface normal. Therefore, we can obtain surface normals of objects by observing the degree of polarization at each surface point. Unfortunately, the correspondence between the degree of polarization and the surface normal is not one to one. Hence, to obtain the correct surface normal, we have to solve the ambiguity problem. In this paper, we introduce a method to solve the ambiguity by comparing the polarization data in two objects, i.e., normal position and tilted with small angle position. We also discuss the geometrical features of the object surface and propose a method for matching two sets of polarization data at identical points on the object surface.     

Online Monitoring of the Degree of Fill in a Rotating Full-Flight Screw of a Corotating Twin-Screw Extruder

It is essential to understand the extent of partial filling of the flight screw, the degree of fill, which is an operational variable of the twin-screw extruder (TSE). This article reports the first attempt to measure, in situ, the degree of fill in a rotating full-flight screw using a specialized light-section method for a TSE. The thickness of the resin sticking to the pushing side decreased with increasing rotational speed. The degree of fill is inversely proportional to the rotational speed and proportional to the feed rate. This result agreed well with the results suggested by the conventional analysis of flow in the TSEs. The fast Fourier transformation of the degree of fill time series indicated that the period of fluctuation correlated with the screw speed rather than the feed rate or throughput. © 2018 American Institute of Chemical Engineers AIChE J, 65: 326–333, 2019     

Sperm Proteases that May Be Involved in the Initiation of Sperm Motility in the Newt,Cynops pyrrhogaster

A protease of sperm in the newt Cynops pyrrhogaster that is released after the acrosome reaction (AR) is proposed to lyse the sheet structure on the outer surface of egg jelly and release sperm motility-initiating substance (SMIS). Here, we found that protease activity in the sperm head was potent to widely digest substrates beneath the sperm. The protease activity measured by fluorescein thiocarbamoyl-casein digestion was detected in the supernatant of the sperm after the AR and the activity was inhibited by 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), an inhibitor for serine or cysteine protease, suggesting the release of serine and/or cysteine proteases by AR. In an in silico analysis of the testes, acrosins and 20S proteasome were identified as possible candidates of the acrosomal proteases. We also detected another AEBSF-sensitive protease activity on the sperm surface. Fluorescence staining with AlexaFluor 488-labeled AEBSF revealed a cysteine protease in the principal piece; it is localized in the joint region between the axial rod and undulating membrane, which includes an axoneme and produces powerful undulation of the membrane for forward sperm motility. These results indicate that AEBSF-sensitive proteases in the acrosome and principal piece may participate in the initiation of sperm motility on the surface of egg jelly.     

Suppression of Lysophosphatidylcholine-Induced Human Aortic Smooth Muscle Cell Calcification by Protein Kinase A Inhibition

Lysophosphatidylcholine (lysoPtdCho) is produced mainly by the phospholipase A2-dependent hydrolysis of phosphatidylcholine (PtdCho) and can induce inflammatory activation and osteogenic gene expression in vascular smooth muscle cells. However, the mechanisms mediating these processes have not been fully elucidated. In this study, we investigated whether inhibition of protein kinase A (PKA) signaling suppressed lysoPtdCho-induced calcification of human aortic smooth muscle cells (HASMC). Calcium levels and alkaline phosphatase activity were significantly increased in HASMC treated with lysoPtdCho, but not PtdCho, compared with those in phosphate-buffered saline-treated HASMC. However, the addition of a PKA inhibitor (H-89) or PKA siRNA blocked lysoPtdCho-induced HASMC calcification. These results showed that lysoPtdCho could activate PKA-mediated HASMC calcification and that PKA may be a therapeutic target for lysoPtdCho-mediated vascular smooth muscle cell calcification.     

ANALYTICAL TREATMENT OF AXISYMMETRICAL THERMOELASTIC FIELD WITH KASSIR'S NONHOMOGENEOUS MATERIAL PROPERTIES AND ITS ADAPTATION TO BOUNDARY VALUE PROBLEM OF SLAB UNDER STEADY TEMPERATURE FIELD

The method of an analytical development of thermoelastic problems for a medium with Kassir's nonhomogeneous material properties is developed. For isothermal problems of such a nonhomogeneous body, an analytical method of development has already been proposed by M. K. Kassir under the assumption that the shear modulus of elasticity G is changed arbitrarily with the variable z of the axial coordinate according to the relation G(z) = G_oz^m. However, the analytical procedure for the thermoelastic field has not been established. In this article, introducing the thermoelastic displacement potential function, the analytical method of development for the axisymmetrical thermoelastic field is established. As an illustrative example, we consider the thermoelastic problem of a slab. Assuming that the shear modulus of elasticity G, the thermal conductivity λ, and the coefficient of linear thermal expansion α vary with the variable [zcirc] of the dimension-less axial coordinate according to the relation G([zcirc]) = G_o[zcirc]^m, λ([zcirc]) = λ₀[zcirc]^l, α([zcirc]) = α₀[zcirc]ⁿ, the axisymmetric temperature solution in a steady state for the slab is obtained and the associated thermal stress components are evaluated theoretically. Numerical calculations are carried out for several cases, taking into account the variety of the nonhomogeneous material properties. Numerical results are shown graphically.     

Characteristic of cylindrical-rotor synchronous generator

It has been observed that the values of the magnetizing reactances in both d- and q-axis are reduced significantly from their corresponding unsaturated values as a result of nonlinearities introduced by saturation under both steady-state and transient operations. In the round rotor synchronous machine, q-axis magnetic circuit saturates appreciably more than that along the d-axis because of the presence of the rotor teeth. In the second section, a new method to calculate the q-axis saturation characteristic from the existing d-axis saturation characteristic has been presented. We have next calculated the saturated values of the d- and q-axis self magnetizing reactances and mutual cross magnetizing reactances between the two orthogonal axes under the steady-state operation. Finally, the effect of saturation, particularly the effect of q-axis saturation, on the power system transient stability has been presented     

Semantic segmentation of trajectories with improved agent models for pedestrian behavior analysis

ABSTRACT

In this paper, we propose a method for semantic segmentation of pedestrian trajectories based on pedestrian behavior models, or agents. The agents model the dynamics of pedestrian movements in two-dimensional space using a linear dynamics model and common start and goal locations of trajectories. First, agent models are estimated from the trajectories obtained from image sequences. Our method is built on top of the Mixture model of Dynamic pedestrian Agents (MDA); however, the MDA's trajectory modeling and estimation are improved. Then, the trajectories are divided into semantically meaningful segments. The subsegments of a trajectory are modeled by applying a hidden Markov model using the estimated agent models. Experimental results with a real trajectory dataset show the effectiveness of the proposed method as compared to the well-known classical Ramer-Douglas-Peucker algorithm and also to the original MDA model.