Characterization of plasma-sprayed and whisker-reinforced alumina coatings

We have strengthened plasma-sprayed alumina coatings by incorporating SiC or Si₃N₄ whiskers. As a result, we found that the whisker-reinforced coatings were greatly improved in properties such as thermal shock resistance and adhesion. Major features of the plasma-sprayed Al₂O₃–5.0 wt % Si₃N₄, coating were investigated by means of scanning electron microscopy, secondary ion mass spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy and thermal radiation measurements.     

Possibility of Superconductivity of the 2212 Phase in the Bi(Pb)-Sr-Ce-Cu-O System

Synthesis of the Bi-2212 compound in the Bi-Sr-Ce-Cu-O system has been already known. But, there has been no report on superconductivity of the compound yet. We have prepared many Bi-2212 samples partially substituted by Pb for Bi in the Bi-Sr-Ce-Cu-O system. The nominal composition is (Bi_2−y Pb _y )Sr₂(Sr_1−x Ce _x )Cu₂O _z . Then, we have investigated possibility of superconductivity for the samples. As a result, we find that a sample with nominal composition ofx=0.23 andy=0.1, which is of almost the single 2212 phase, shows an anomaly at about 70 K in addition to temperature dependence of the resistivity like a semiconductor. Furthermore, the sample also shows a decrease of magnetic susceptibility starting at about 70 K with decreasing temperature. These experimental results can be considered to result from superconductivity of the 2212 phase in the Bi(Pb)-Sr-Ce-Cu-O system.     

A new approach for evaluating crack growth resistance curve of mode II delamination by doubly end-notched tension tests

Quantitative determination of interlaminar fracture toughness that governs onset and growth of delamination is essential for engineering of composite materials and structures. This study proposes a new approach to evaluate both the initial fracture toughness and the crack growth resistance property of pure mode II delamination by tensile tests of specimens having two initial cracks, which were conceived from double-lap joints. The proposed test method achieves stable growth of mode II delamination using a fundamental testing system. This study presents the specimen configuration, the theory to evaluate the energy release rate, and experiment results. The mode II initial fracture toughness measured by the present approach agreed well with the results of conventional end-notched flexure tests. Furthermore, the crack growth resistance curves were evaluated by unloading-reloading tests of the proposed doubly end-notched tension specimens.     

Translating Multi-Agent Autoepistemic Logic into Logic Program

In order to develop a proof procedure of multi-agent autoepistemic Logic (MAEL), a natural framework to formalize belief and reasoning including inheritance, persistence, and causality, we introduce a method that translates a MAEL theory into a logic program with integrity constraints. It is proved that there exists one-to-one correspondence between extensions of a MAEL theory and stable models of a logic program translated from it. Our approach has the following advantages: (1) We can obtain all extensions of a MAEL theory if we compute all stable models of the translated logic program. (2) We can fully use efficient techniques or systems for computing stable models of a logic program. We also investigate the properties of reasoning in MAEL through this translation. The fact that the extension computing problem can be reduced to the stable model computing problem implies that there are close relationships between MAEL and other formalizations of nonmonotonic reasoning.     

Load Sharing Behavior of Star Gearing Reducer for Geared Turbofan Engine

Load sharing behavior is very important for power-split gearing system, star gearing reducer as a new type and special transmission system can be used in many industry fields. However, there is few literature regarding the key multiple-split load sharing issue in main gearbox used in new type geared turbofan engine. Further mechanism analysis are made on load sharing behavior among star gears of star gearing reducer for geared turbofan engine. Comprehensive meshing error analysis are conducted on eccentricity error, gear thickness error, base pitch error, assembly error, and bearing error of star gearing reducer respectively. Floating meshing error resulting from meshing clearance variation caused by the simultaneous floating of sun gear and annular gear are taken into account. A refined mathematical model for load sharing coefficient calculation is established in consideration of different meshing stiffness and supporting stiffness for components. The regular curves of load sharing coefficient under the influence of interactions, single action and single variation of various component errors are obtained. The accurate sensitivity of load sharing coefficient toward different errors is mastered. The load sharing coefficient of star gearing reducer is 1.033 and the maximum meshing force in gear tooth is about 3010 N. This paper provides scientific theory evidences for optimal parameter design and proper tolerance distribution in advanced development and manufacturing process, so as to achieve optimal effects in economy and technology.     

Simulation for radiolytic products of seawater: effects of seawater constituents,dilution rate,and dose rate

Radiolysis calculations of simulated seawater were conducted using reported data on chemical yields and chemical reaction sets to predict the effects of seawater constituents on water radiolysis. Hydrogen, oxygen, and hydrogen peroxide were continuously produced from simulated seawater during γ-ray irradiation. The concentration of H₂ exceeded its saturation concentration before it reached the steady-state concentration. The production behavior of these molecules was significantly promoted by the addition of bromide ions (Br^?) because of the high reactivity of Br^? with the hydroxyl radical, an effective hydrogen scavenger. It is also shown that the concentrations of these molecules were effectively suppressed by diluting seawater constituents by less than 1%.     

Phase appearance during polymerization of fluorinated polyimide monomers and deposition into the microscopic‐scale trenches in supercritical carbon dioxide

The phase appearance during the synthesis of fluorinated polyamic acid (PAA) from 2,2‐bis(3,4‐anhydrodicarboxyphenyl)‐hexafluoropropane (6FDA) and 2,2′‐bis(trifluoromethyl)?4,4′‐diaminobiphenyl (TFDB) in supercritical carbon dioxide (scCO₂) was investigated to obtain fundamental data for the deposition of fluorinate polyimides (PI) using scCO₂. All polymerizations were carried out at 30 MPa for 60 min. The experimental temperatures ranged from 50 to 70 °C, and each of the monomer concentrations ranged from 0.67 × 10^?5 to 3.3 × 10^?5 mol cm^?3. The holding time of the transparent phases, which was the time from the beginning of the polymerization to the appearance of a turbid phase, was increased with either a decrease in the polymerization temperature or a decrease in the initial monomer concentration. The holding time of the fluorinated PAA was longer than that of the monomers of Kapton‐type PAA. The deposition of PI into the microscopic‐scale trenches that had formed on the silicon wafer was successful in scCO₂. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43334.     

Influence on the propulsive performance due to the difference in the fin shape of a robotic manta

This paper experimentally investigates the influence on the propulsive performance by the difference in the fin shape of a robotic manta. Five kinds of fin shapes, i.e., a rectangle, a triangle, a trapezoid, and two right triangles, are used in experiment to measure the forward speed of the robot, where two types of right triangle are discriminated, depending on the arrangement of the right angle part and each fin area is assumed to be approximately equal, and the number of fin rays is the same at all the fins. It is proved that a significant difference in propulsive speed arises depending on the difference in the fin shape. Some experiments are additionally conducted to examine the influence on the propulsive speed and its efficiency, due to the parameter change of a progressive wave in the fin.     

Visibility Enhancement using Autonomous Multicamera Controls with Situational Role Assignment for Teleoperated Work Machines

The aim of this study is to provide a machine operator with enhanced visibility and more adaptive visual information suited to the work situation, particularly advanced unmanned construction. Toward that end, we propose a method for autonomously controlling multiple environmental cameras. Situations in which the yaw, pitch, and zoom of cameras should be controlled are analyzed. Additionally, we define imaging objects, including the machine, manipulators, and end points; and imaging modes, including tracking, zoom, posture, and trajectory modes. To control each camera simply and effectively, four practical camera roles with different combinations of the imaging objects and modes were defined: overview machine, enlarge end point, posture‐manipulator, and trajectory‐manipulator. A real‐time role assignment system is described for assigning the four camera roles to four out of six cameras suitable for the work situation (e.g., reaching, grasping, transport, and releasing) on the basis of the assignment‐priority rules. To test this system, debris‐removal tasks were performed in a virtual reality simulation to compare performance among fixed camera, manual control camera, and autonomous control camera systems. The results showed that the autonomous system was the best of the three at decreasing the number of grasping misses and erroneous contacts and simultaneously increasing the subjective usability and time efficiency.     

“My child will be respected”: Parental perspectives on computers and education in Rural India

Public spending on computer centers in rural Indian public schools raise questions about the value of expensive modern technology in extremely resource-strapped environments. Arguments for or against providing computers in low-income schools have appeared in policy circles, academia, teacher conferences, and philanthropic discussions, with passionate rhetoric from all sides. We present the results of a qualitative study of computer-aided learning centers in schools catering primarily to Below Poverty Line (BPL) families in four districts of rural Karnataka, South India. Here, we held a series of open-and close-ended discussions with parents of children from these schools on issues such as aspirations, quality of schooling, and the perception of computers more generally. The research reveals a range of voices on hopes for the next generation, perceived value of computer courses and higher education, and the perceived changes in villages after the arrival of computers in their local schools. It emerges that for many parents, the computer has an immense symbolic value—separate from its functional value—that is tied to social and economic ascendancy. We find that this symbolic value derives from associations that parents imbibe from their various interactions with people using computers in a range of situations. We find in our interviews a heightened sense of mystique over the technology and its potential, across people with varying levels of first-hand experience and understanding of computers. We find that notions of change and hope are situated within an environment of great fear about the future of agriculture. We argue here that this, alongside a widespread existing discourse about computers in media and public life in India, mostly emerging from urban middle-classes ideas around technology, help spur a strong sense of expectation that the computers can dramatically change social prospects even among the poorest and most excluded. From competing with English as the gateway to power, to impacting dowry costs for female youth, interviews show a myriad of expectations from technology, creating what we see as a strong case for a nuanced look at the discourse and mythology of computers and technology in developing regions.