TEM method for rapid and precise evaluation of continuous recrystallization

With the aid of a double-tilt holder in a transmission electron microscope, a new method for a rapid and precise determination of the misorientations of a large number of subgrain or grain boundaries is given in this article. By use of the method, the continuous recrystallization can be rapidly and precisely evaluated when compared to the other conventional methods.     

Bridging stresses in sintered reaction-bonded Si3N4 from COD measurements

Crack opening displacement measurements on a sintered reaction-bonded Si₃N₄ ceramic obtained in bending tests with edge-V-notched specimens were evaluated. A procedure is proposed which allows a straight-forward evaluation of the experimental results in order to obtain the bridging stresses as a function of crack opening displacements. Bridging stresses up to 160 MPa were found acting over a distance of about 0.4 μm. In addition crack profile measurements were performed for Vickers indentation cracks which could approximately be described by use of the bridging relation obtained.     

An anti-windup strategy for active vibration isolation systems

An anti-windup augmentation technique for active vibration isolation systems is considered in this paper and shown to lead to high-performance vibration isolation through simulations and experiments. First, the anti-windup construction is described and desirable properties of the augmented closed-loop system are illustrated. Then, the anti-windup technique is tested on a simulation example and finally shown to perform excellently on a commercial vibration isolation device: Newport Corporation's Elite 3^TM active vibration isolation system which has been patented and is now commercialized with this architecture. Both simulation and experimental results confirm the effectiveness of the anti-windup scheme.     

Development of a small DMFC bipolar plate stack for portable applications

The direct methanol fuel cell (DMFC) is regarded as a promising candidate in portable electronic power applications. Bipolar plate stacks were systematically studied by controlling the operating conditions, and by adjusting the stack structure design parameters, to develop more commercial DMFCs. The findings indicate that the peak power of the stack is influenced more strongly by the flow rate of air than by that of the methanol solution. Notably, the stack performance remains constant even as the channel depth is decreased from 1.0 to 0.6 mm, without loss of the performance in each cell. Furthermore, the specific power density of the stack was increased greatly from ∼60 to ∼100 W l⁻¹ for stacks of 10 and 18 cells, respectively. The current status of the work indicates that the power output of an 18-cell short stack reaches 33 W in air at 70 °C. The outer dimensions of this 18-cell short stack are only 80 mm × 80 mm × 51 mm, which are suitable for practical applications in 10–20 W DMFC portable systems.     

Experimental investigation of the normal spectral emissivity and other thermophysical properties of pulse-heated Ni-Ti and Au-Ni alloys into the liquid phase

1. Introduction Metal working industry needs accurate thermo- physical properties of liquid metals and alloys as input data for different simulation routines to im- prove the performance of their products. Within this paper we continue the systematic investigation of the dependence of emissivity of binary alloys on the relative concentration of the constituent elements (for a previous paper see [1]). 2. Experimental method A fast ohmic pulse heating technique is applied to heat metallic wire-s…     

Improved durability of Si/B/N/C random inorganic networks

The inherent high temperature durability as well as the hardness of random inorganic networks composed of Si, B, N and C, can be raised through the incorporation of rigid structural elements (e.g. borazine rings) as well as through an increase of the carbon content. This has been shown by comparison of the high temperature durabilities and micromechanical properties of newly synthesized Si/B/N/C ceramics derived from different acyclic and cyclic single source precursors. Crosslinking of these specially designed monomers with methylamine provides highly homogeneous preceramic polymers, in which the predetermined structural features of the molecular precursors are embedded. Subsequent pyrolysis and calcination up to 1500 °C converts the polymers into all-inorganic amorphous silicon boron carbonitrides. Depending on the constitution of the precursors, the as-obtained materials exhibit a combination of a high carbon content together with borazine rings embedded into the covalent network. Comparing the high temperature stability, hardness and stiffness of the synthesized ceramics, the best performance is achieved when carbon rich borazine derivatives are employed as single source precursors. Thus, the high temperature durability can be raised up to at least 2000 °C, and, at the same time, the microhardness and elastic modulus is maximized up to 14.5 and 127 GPa, respectively. The new materials have been characterized by IR spectroscopy, elemental analysis, XRD, SEM, DTA/TG, and by nanoindentation.     

Sensor fault tolerant control using sliding mode observers

Previous work has considered the use of sliding mode observers for fault detection and isolation (FDI) in uncertain linear systems whereby the unknown faults are reconstructed by appropriate processing of the so-called equivalent output error injection. The paper builds on this work and considers such a scheme within the broader context of fault tolerant control. Specifically, by correcting the faulty measurement by an estimate of the fault obtained from the sliding mode FDI scheme, good closed-loop performance is still maintained. An example of such a scheme, which has been implemented in real-time on a laboratory dc motor rig, is described.     

SA299钢冷脆行为的研究

某锅炉厂生产的锅炉汽包,在冬季制造过程中发生破裂,汽包材料为 SA299钢,对断口的初步分析发现为脆性解理断口,据此认为是冷脆破坏。本文依据冷脆特征温度 Tc 的概念对 SA299钢的冷脆行为进行了细致的分析。