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31.
Fracture mechanics and crack contact analyses of the active repair of multi-layered piezoelectric patches bonded on cracked structures 总被引:1,自引:0,他引:1
In this paper, two-dimensional plane strain finite element analyses of the active repair for cracked structures by using multi-layered piezoelectric patches have been studied. The reductions of stress intensity factors and strain energy density factor at the crack tips are obtained. Also, the repair voltages for various conditions are obtained for estimating the repair performances. Lower repair voltage is a better choice because it is low-energy-consuming and safer for the operation. From the results of numerical fracture mechanics, it shows the crack contact conditions must be considered in the analysis. However, the friction on the crack has few effects on the repair performances for this mode-I dominated case. The better design choices for the piezoelectric patch are as follows: increasing the layer number, increasing the patch length, and reducing the patch thickness. In additions, it is not a good idea to use higher input voltage that is larger than the repair voltage because it will enlarge the crack open near the crack tip. Too long patch length has no advantage for the active repair. 相似文献
32.
This paper describes a new theoretical approach to bone microdamage, in which a population of cracks is explicitly modelled. A given sample of bone is assumed to contain a certain number of cracks, whose growth characteristics are described with an equation containing stochastic variables to create statistical differences from one crack to another. This type of model allows us to predict a wide variety of data. The present paper illustrates the different types of prediction which can be made, including: (i) standard damage parameters such as the number and length of cracks and the reduction in stiffness; (ii) fatigue test data such as the number of cycles to failure as a function of stress level, including scatter; (iii) effects due to the living system, including repair, remodelling and adaptation. A useful feature of the model is our ability to examine the statistics of the crack population in detail to find, for example, the number of cracks which are potentially dangerous as opposed to those which are dormant, and to investigate the reasons for increased crack numbers in the bones of older people. The potential also exists to use the model to investigate different theories of bone remodelling and adaptation. 相似文献
33.
The photooxidation of adenosine in presence of peroxydisulphate (PDS) has been studied by spectrophotometrically measuring
the absorbance of adenosine at 260 nm. The rates of oxidation of adenosine by sulphate radical anion have been determined
in the presence of different concentrations of caffeic acid. Increase in [caffeic acid] is found to decrease the rate of oxidation
of adenosine suggesting that caffeic acid acts as an efficient scavenger of SO
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and protects adenosine from it. Sulphate radical anion competes for adenosine as well as for caffeic acid. The quantum yields
of photooxidation of adenosine have been calculated from the rates of oxidation of adenosine and the light intensity absorbed
by PDS at 254 nm, the wavelength at which PDS is activated to sulphate radical anion. From the results of experimentally determined
quantum yields (Φexpt1) and the quantum yields calculated (Φcal) assuming caffeic acid acting only as a scavenger of SO
4
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show that Φexpt1 values are lower than Φexpt1 values. The ǵf values, which are experimentally found quantum yield values at each caffeic acid concentration and corrected
for
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scavenging by caffeic acid, are also found to be greater than Φexpt1 values. These observations suggest that the transient adenosine radicals are repaired by caffeic acid in addition to scavenging
of sulphate radical anions. 相似文献
34.
As markets have become more and more competitive, disorder has become a prevailing characteristic of modern production systems that are operating in complex, dynamic and uncertain environments. Minimizing disorder in these production systems requires stringent control measures by management, with costs that are usually hidden or difficult to estimate. Not accounting for these costs leads to less efficient production systems. This paper postulates that the behaviour of production systems very much resembles that of physical systems. Such a parallel suggests that improvements to production systems may be achievable by applying the first and second laws of thermodynamics to reduce system entropy (or disorder). The applicability of these laws is demonstrated in a simple reverse supply chain context, where products are collected and later repaired at some rate while other products might be disposed outside according to some waste disposal rate. Numerical examples are provided. 相似文献
35.
Luigi Portinale Daniele Codetta Raiteri 《International Journal of Approximate Reasoning》2010,51(2):179-195
In this paper, we present an approach to reliability modeling and analysis based on the automatic conversion of a particular reliability engineering model, the Dynamic Fault Tree (DFT), into Dynamic Bayesian Networks (DBN). The approach is implemented in a software tool called RADYBAN (Reliability Analysis with DYnamic BAyesian Networks). The aim is to provide a familiar interface to reliability engineers, by allowing them to model the system to be analyzed with a standard formalism; however, a modular algorithm is implemented to automatically compile a DFT into the corresponding DBN. In fact, when the computation of specific reliability measures is requested, classical algorithms for the inference on Dynamic Bayesian Networks are exploited, in order to compute the requested parameters. This is performed in a totally transparent way to the user, who could in principle be completely unaware of the underlying Bayesian Network. The use of DBNs allows the user to be able to compute measures that are not directly computable from DFTs, but that are naturally obtainable from DBN inference. Moreover, the modeling capabilities of a DBN, allow us to extend the basic DFT formalism, by introducing probabilistic dependencies among system components, as well as the definition of specific repair policies that can be taken into account during the reliability analysis phase. We finally show how the approach operates on some specific examples, by describing the advantages of having available a full inference engine based on DBNs for the requested analysis tasks. 相似文献
36.
S. Yamasaki M. Iwakuma K. Funaki J. Kato T. Chikumoto K. Tanabe K. Nakao T. Izumi Y. Yamada Y. Shiohara T. Saito 《Physica C: Superconductivity and its Applications》2010,470(20):1316-1320
For near-future applications of REBa2Cu3O7 (REBCO) coated conductors to electric power cables, transformers and Superconducting Magnetic Energy Storage (SMES), the long taped wires with high performance in the transport properties have been designed and fabricated. Moreover, in order to drastically reduce AC losses in perpendicular field configuration, advanced multifilament YBCO coated conductors (MFYCCs) fabricated with technique of a laser scribing process have been also developed. In the present study, from engineering viewpoints to utilize such advanced conductors, we evaluated the transport and AC loss properties of short MFYCCs with a repaired part or a joint by a diffusion joint technique with the saddle-shaped pickup coil method. 相似文献
37.
The locality of locally repairable codes (LRCs) for a distributed storage system is the number of nodes that participate in the repair of failed nodes, which characterizes the repair cost. In this paper, we first determine the locality of MacDonald codes, then propose three constructions of LRCs with . Based on these results, for and , we give an optimal linear code with small locality. The distance optimality of these linear codes can be judged by the codetable of M. Grassl for and by the Griesmer bound for . Almost all the codes () have locality except for the three codes, and most of the code with achieves the Cadambe–Mazumdar bound for LRCs. 相似文献
38.
In order to evaluate the seismic performance of damaged reinforced concrete members, particularly bridge piers, an inelastic
time-dependent element is proposed. The proposed element enables increased characteristics due to structural intervention
(i.e., repair or retrofitting) to be accurately reflected in the degraded strength and stiffness of the members. The inelastic
time-dependent element having both birth and death times can freely be activated within the user-defined time intervals of
interest during static and dynamic time-history analyses. Comparative studies are carried out for reinforced concrete bridge
columns that are repaired and retrofitted. Analytical predictions incorporating the developed element show reasonable correlation
with experimental results. Also conducted is a nonlinear time-history analysis of a reinforced concrete bridge under multiple
earthquakes. Comparative analytical results confirm the applicability and effectiveness of the current development. It is
thus expected that the present element is capable of providing salient features for the healthy evaluation of seismic performance
of reinforced concrete members being repaired and retrofitted. 相似文献
39.
Liliana S. O. Silva Pedro M. Matias Clia V. Romo Lígia M. Saraiva 《Molecules (Basel, Switzerland)》2022,27(13)
Repair of Iron Center proteins (RIC) form a family of di-iron proteins that are widely spread in the microbial world. RICs contain a binuclear nonheme iron site in a four-helix bundle fold, two basic features of hemerythrin-like proteins. In this work, we review the data on microbial RICs including how their genes are regulated and contribute to the survival of pathogenic bacteria. We gathered the currently available biochemical, spectroscopic and structural data on RICs with a particular focus on Escherichia coli RIC (also known as YtfE), which remains the best-studied protein with extensive biochemical characterization. Additionally, we present novel structural data for Escherichia coli YtfE harboring a di-manganese site and the protein’s affinity for this metal. The networking of protein interactions involving YtfE is also described and integrated into the proposed physiological role as an iron donor for reassembling of stress-damaged iron-sulfur centers. 相似文献
40.