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161.
Kitakami O. Ogawa Y. Fujiwara H. Kugiya F. Suzuki M. 《IEEE transactions on magnetics》1989,25(3):2607-2611
A Co-Cr film deposited directly on a substrate has an initial growth layer with low coercivity. However, the existence of a Ti underlayer prevents the formation of such a layer. As a result, Co-Cr film deposited on a Ti underlayer has high perpendicular anisotropy and coercivity even in cases of extremely thin film thickness (200 Å). As for the read-write characteristics of Co-Cr thin-film media, the existence of such an initial growth layer greatly improves the reproduced output level. The cause for this is considered to be that the free charges which appear on the back surface of the perpendicular recording layer are reduced and the demagnetization field acting on the recorded magnetization subsequently decreases due to the existence of the initial growth layer 相似文献
162.
H.U. Wider 《Nuclear Engineering and Design》1987,101(3)
Transient fuel pin behaviour and fuel motion models are of major importance for the analysis of the initiation phase of unprotected whole-core LOF and TOP accidents in LMFBRs. The role played by these models is highlighted by discussing LOF and TOP accident sequences. This is followed by an overview of present whole-core fuel pin behaviour and fuel motion models and also a critical evaluation of these models. 相似文献
163.
Static light scattering was used to investigate dilute dispersions of fine gamma -Fe/sub 2/O/sub 3/ magnetic particles. The particles were acicular and on average 0.39 mu m long and 0.056 mu m in diameter. They were dispersed in organic solvents at concentrations of approximately 10/sup -4/ vol%, corresponding to an average interparticle separation of 9 mu m. Computer programs using a coupled dipole algorithm to predict the scattering from the particles were written. Experimental results do not agree with computer calculations of the light scattering from single particles, but are consistent with scattering from thick ropelike agglomerates of particles. The size of these agglomerates was estimated after 10 s to be less than 100 particles, while the thickness of the ropes is at least 5 particles.<> 相似文献
164.
Physical and process manufacturing factors affecting the properties of particleboard were examined and mathematical relationships were derived to predict board modulus of elasticity and internal bond. The equations, derived from a series of previous laboratory investigations, allow the simulation of the effects of various process conditions on final properties of 1/2-inch (12-mm) boards. 相似文献
165.
A digital signal processor-based control system for the permanent magnet-assisted reluctance synchronous machine, with the emphasis on dynamic performance, is proposed. A classical design approach is used to design the current and speed controllers for the machine. The stator current of the machine is controlled in such a way that the current angle in the dq synchronous reference frame is constant. The load-torque is estimated using a state space observer and compensation current based on the estimated load is used to improve the dynamic performance of the drive. The control system design is machine specific as it relies on data from finite-element analysis. Simulated and measured results on a 110-kW power level show that the resulting control system is stable and robust with good dynamic performance 相似文献
166.
The dynamic response of highway bridges subjected to moving truckloads has been observed to be dependent on (1) dynamic characteristics of the bridge; (2) truck configuration, speed, and lane position on the bridge; and (3) road surface roughness profile of the bridge and its approach. Historically, truckloads were measured to determine the load spectra for girder bridges. However, truckload measurements are either made for a short period of time [for example, weigh-in-motion (WIM) data] or are statistically biased (for example, weigh stations) and cost prohibitive. The objective of this paper is to present results of a 3D computer-based model for the simulation of multiple trucks on girder bridges. The model is based on the grillage approach and is applied to four steel girder bridges tested under normal truck traffic. Actual truckload data collected using a discrete bridge WIM system are used in the model. The data include axle loads, truck gross weight, axle configuration, and statistical data on multiple presence (side by side or following). The results are presented as a function of the static and dynamic stresses in each girder and compared with code provisions for dynamic load factor. The study provides an alternate method for the development of live-load models for bridge design and evaluation. 相似文献
167.
Reaction models are proposed to quantify the hydration products and to determine the composition of C–S–H from alkali-activated
slags (AAS). Products of the slag hydration are first summarized from observations in literature. The main hydration products
include C–S–H, hydrotalcite, hydrogarnet, AFm phases (C4AH13 and C2ASH8) and ettringite. Then, three stoichiometric reaction models are established correlating the mineral composition of slag (the
glass part) with the hydration products. Using the proposed models, quantities of hydration products and composition of C–S–H
are determined. The models are validated with a number of experimental investigations reported in literature, yielding good
agreement, i.e., these models can successfully predict the hydration reaction of AAS. The models are furthermore applied to
calculate the retained water in the hydration products of AAS in different hydration states and a general hydration equation
of AAS is derived. As an illustration to one of the model applications, chemical shrinkage of the AAS cement paste in different
hydration states are predicted. The chemical shrinkage of AAS is shown to be remarkably higher than OPC. Furthermore, phase
distribution in the hardened AAS paste and the porosity are calculated. 相似文献
168.
On structural and high temperature electrochemical properties of ZrO2 thin film coating on Zr metal produced by carbonate melt 总被引:1,自引:0,他引:1
Melt of NaCO3 can favor oxidation of Zr to form ZrO2 thin film on Zr surface, which is used to make Zr/ZrO2 oxidation/reduction electrode of pH sensor for testing elevated temperature aqueous solutions. Using SEM, EPMA, XPS, EXAFS
and HRTEM, we found that ZrO2 film is tightness and solid with 20 μm thickness composed by nanometer-sized monoclinic crystals. Zr/ZrO2 interface is characterized of zoning structure according to topography and chemical composition in five zones: oxygen-rich
ZrO2, ZrO2, oxygen-rich Zr metal, oxygen-bearing Zr and Zr from outmost to center. Melt oxidation process of Zr involved oxidation time,
air and temperature. The air is important effect on structural and electrochemical properties of ZrO2 thin film for making elevate temperature electrochemical sensor. If oxygen air largely presented in carbonate melting process,
ZrO2 thin film is not tightness and not for oxidation/reduction electrode. 相似文献
169.
Z. Ferhat-Hamida H. Phuong-Nguyen P. Bernazzani A. Haine G. Delmas 《Journal of Materials Science》2007,42(9):3138-3154
LLDPE samples synthesized with Ziegler–Natta (ZN) and Metallocene (MT) catalysts have been analyzed to investigate a potential
catalyst-dependent morphology and to find an explanation for the difficult processing of MT. Slow calorimetry at v = 0.02 K/min and IR at RT and in the melt are used. The differences between MT and ZN are assigned to their different composition,
MT not having the linear segments, which are present in ZN. Slow calorimetry is effectively a drawing process of the melt
with chain orientation followed by decay. The later event, characterized by an endotherm, ΔH
network, occurs at higher temperatures for MT, the presence of a regular distribution of methyl groups slowing down the process.
The rocking, gauche, bending and stretching regions of the IR spectra are analyzed. The nascent MT has more strained bands
in the rocking region. The wagging region reveals the more homogeneous environment of MT through the maximum absorbance at
1,368 cm−1. Decomposition of bands is made for the rocking and wagging regions. The orthorhombic crystallinity, αc (FTIR), measures the sum of long- and short-range orthorhombic order, the latter being obtained by αc (FTIR)-αc (X-rays). The values of αc (FTIR) for MT and ZN are very similar in conditions of equilibrium. The justifications for the molecular origin of ΔH
network are presented: (i) the slow relaxation of long chains strained and oriented in the melt measured by other techniques, (ii)
The correlation, for gels of a linear sample, made in different solvents, between the maximum drawability, λmax, and ΔH
network in a slow T-ramp. The range is 80–270 for λmax and 40–120 J/g for ΔH
network. (iii) The comparison of two traces of the same sample, between 140 °C and 270 °C, show that comparable events in the melt
appear in the integrated absorbance and in the slow calorimetry signal. Analysis on thin films of the little-studied CH2 stretching region reveals that their extinction coefficient, ε, and the shape of the bands are highly sensitive to the sample
history, ε diminishing by a large factor in slowly crystallized samples. Events in the slow T-ramp, followed by a fast crystallization, on the other hand, leads to materials with standard characteristics. Slow calorimetry
traces display more events (endothermic and exothermic) for MT than for ZN, a finding consistent with more flow irregularities
during processing. Equilibrium conditions and better processing could be reached for MT by extending time in the melt or using
higher temperatures. 相似文献
170.
I.H. Song 《Thin solid films》2007,515(19):7598-7602
This paper is a report on the effect of a single perpendicular grain boundary on the hot-carrier and high current stability in high performance polycrystalline silicon (poly-Si) thin film transistors (TFTs). Under a hot carrier stress condition (Vg = Vth + 1 V, Vd = 12 V), the poly-Si TFT with a single grain boundary is superior to the poly-Si without any grain boundary because of the smaller free carriers available for electric conduction. The shift of transconductance in poly-Si TFT with a single grain boundary is less than 5% after hot carrier stress during a period of 1000 s. The shift of transconductance is about 25% in the case of the poly-Si TFTs without a grain boundary in the channel. On high current stress, the poly-Si TFT without the grain boundary is less degraded than the poly-Si TFT with the grain boundary because the concentrated electric field near the drain junction is lower. 相似文献