342 research outputs found
Energy Distribution in Electrical Discharge Machining with Graphite Electrode
In EDM, the machining characteristics greatly depend on the energy distribution. Therefore, it is very important to clarify the energy distribution for understanding various phenomena in EDM. In this paper, the energy distribution in EDM with graphite electrode is investigated by measuring the temperatures of electrode and workpiece. Experimental analysis shows that the material removal rate depends on energy density while the electrode wear greatly depends on the adhesion of heat resolved carbon from machining fluid, and the energies distributed into electrode and workpiece are almost constant regardless of pulse duration
The Effect of Electrode Polarity on Electrical Discharge Machining Performance in Water
Practical utilization of ram type electrical discharge machining in uninflammable fluid has been expected in place of inflammable kerosine type fluid for unmanned operation in a workshop. The electrical discharge machining performance in deionized water is experimentally investigated on the basis of the analysis of the crater generated by a single pulse discharge. The experimental analysis makes it clear that the electrical discharge machining performance in deionized water is greatly affected by the electrode polarity. The metal removal rate in the normal polarity machining is higher than that in reverse polarity machining, while the electrode wear rate in the normal polarity machining is greater than that in reverse polarity machining. Therefore the electrode polarity should be properly selected according to the purpose of machining
Bi-stability of mixed states in neural network storing hierarchical patterns
We discuss the properties of equilibrium states in an autoassociative memory
model storing hierarchically correlated patterns (hereafter, hierarchical
patterns). We will show that symmetric mixed states (hereafter, mixed states)
are bi-stable on the associative memory model storing the hierarchical patterns
in a region of the ferromagnetic phase. This means that the first-order
transition occurs in this ferromagnetic phase. We treat these contents with a
statistical mechanical method (SCSNA) and by computer simulation. Finally, we
discuss a physiological implication of this model. Sugase et al. analyzed the
time-course of the information carried by the firing of face-responsive neurons
in the inferior temporal cortex. We also discuss the relation between the
theoretical results and the physiological experiments of Sugase et al.Comment: 18 pages, 6 figure
Three-dimensional crystalline carbon: Stable polymers of C20 fullerene
We report on a first-principles total-energy calculation that provides the energetics and electronic structure of stable polymerized fullerites consisting of the smallest fullerene C20. We find that the C20 fullerene has periodic three-dimensional covalent networks with orthorhombic and tetragonal symmetries. Both are found to be energetically stable and to be elemental semiconductors with a moderate energy gap of about 1.5 eV. Substantially high peaks of the density of states are found to appear below the top of the valence band, suggesting that these materials under hole-doped conditions are candidates for superconductors
Neural-humoral responses during head-up tilt in healthy young white and black women
Young black women have higher prevalence of hypertension during pregnancy compared to white women, which may be attributable to differences in blood pressure (BP) regulation. We hypothesized that young normotensive black women would demonstrate augmented muscle sympathetic nerve activity (MSNA) and renal-adrenal responses to orthostasis. Fifteen white and ten black women (30 ± 4 vs. 32 ± 6 years; means ± SD) had haemodynamics and MSNA measured during baseline (BL), 30 and 60° head-up tilt (HUT), and recovery. Blood was drawn for catecholamines, direct renin, vasopressin, and aldosterone. BL brachial systolic BP (SBP: 107 ± 6 vs. 101 ± 9 mmHg) and diastolic BP (DBP: 62 ± 4 vs. 56 ± 7 mmHg) were higher in white women (both p < 0.05). Δ DBP (60° HUT-BL) was greater in black women compared to white (p < 0.05). Cardiac output and total peripheral resistance were similar between groups. MSNA burst frequency was higher in whites (BL: 16 ± 10 vs. 14 ± 9 bursts/min, main effect p < 0.05) and increased in both groups during HUT (60°: 39 ± 8 vs. 34 ± 13 bursts/min, p < 0.05 from BL). Noradrenaline was higher in white women during 60° HUT (60° HUT: 364 ± 102 vs. 267 ± 89 pg/ml, p < 0.05). Direct renin was higher and vasopressin and Δ aldosterone tended to be higher in blacks (BL, direct renin: 12.1 ± 5.0 vs. 14.4 ± 3.7 pg/ml, p < 0.05; BL, vasopressin: 0.4 ± 0.0 vs. 1.6 ± 3.6 pg/ml, p = 0.065; Δ aldosterone: −0.9 ± 5.1 vs. 3.8 ± 7.5 ng/ml; p = 0.069). These results suggest that young normotensive white women may rely on sympathetic neural activity more so than black women who have a tendency to rely on the renal-adrenal system to regulate BP during an orthostatic stress
Micro-Welding Of High Thermal Conductive Material Aluminum-Graphite Composite By Pulsed ND:YAG Laser.
The development of advanced materials with superior high thermal properties and high specific strength has led to new metal matrix composites (MMCs) as a great attractive material in electrical and electronic industries. In order to manufacture more practical component from MMCs, a tech-nique for joining MMCs to other similar composites or monolithic materials is strongly required. Therefore, the reliable and economic joining technique is investigated to increase the applications of MMCs. In this study, the overlap welding of pure aluminum and super thermal conductive (STC) aluminum-graphite composite was experimentally and numerically investigated by using a pulsed Nd:YAG laser. In order to discuss the welding of dissimilar materials with different thermophysical properties, the temporal change of heat input was controlled by arranging the laser pulse waveform. The porosities and bumps were observed as the remarkable weld defects in the welding process without a pulse control. On the other hand, the weld bead was largely free of defects, and a size of bump was relatively small with the appropriate controlled pulse waveform. It was clarified that the laser welded joint of an aluminum and a STC aluminum-graphite composite could be successfully achieved with the better weld penetration stability by the appropriate controlled pulse waveform
Nondestructive structure test of cam-shaft using both eddy current and X-rays
The cam-shaft for the internal-combustion engine needs to be chilled at the foundry stage to rise the cam hardness, but unexpected chilled structures could occur on the sensor plate surface. If chilled structures exist on the sensor plate, a grinding tool may break when grinding sensor plate, or the specified shape may be unable to be produced due to resistance arising from the hyper-hardness of the chilled structures. For this reason, developing an inspection technique and a device for detecting unnecessary chilled structures before grinding the cam-shaft and for determining the rejection and removal of cam-shafts with chilled structures detected was necessary. This article reports on a recently developed nondestructive method using an eddy current test and X-rays to accurately detect chilled structures on a cam-shaft sensor plate. © (2012) Trans Tech Publications, Switzerland
Complete Genome Sequence of the Marine Carbazole-Degrading Bacterium Erythrobacter sp. Strain KY5
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