Inelastic constitutive equation of plasma-sprayed ceramic thermal barrier coatings

Ceramic thermal barrier coatings (TBCs) are a very important technology for protecting the hot parts of gas turbines (GTs) from a high-temperature environment. The coating stress generated in the operation of GTs brings cracking and peeling damage to the TBCs. Thus, it is necessary to evaluate precisely such coating stress in a TBC system. We have obtained a stress-strain curve for a freestanding ceramic coat specimen peeled from a TBC coated substrate by conducting the bending test. The test results have revealed that the ceramic coating deforms nonlinearly with the applied loading. In this study, an inelastic constitutive equation for the ceramic thermal barrier coatings deposited by APS is developed. The obtained results are as follows: (1) the micromechanics-based constitutive equation was formulated with micro crack density formed at splat boundary, and (2) it was shown that the numerical results for a nonlinearly deformed beam simulated by the developed constitutive equation agreed with the experimental results obtained by cantilever bending tests.     

The use of a figure-of-eight coil for fibre optic respiratory plethysmography: Geometrical analysis and experimental characterisation

An optical fibre sensor based on the macro-bending loss effect has been redeveloped for thoracic and abdominal circumference measurements in non-invasive plethysmographic respiratory monitoring. A new geometrical analysis of the figure-of-eight transducer is presented, along with an optical analysis, and experimental results are presented which are in good agreement with these analyses. A comparison is made with earlier implementations of macrobending loss effect based transducers for respiratory measurement, and the newer sensor compares favourably, indicating a higher resolution and a simpler mechanical construction.     

Block-based motion field segmentation for video coding

In the past few years, motion compensation has been widely used in the coding of image sequences. Most of motion estimation and compensation schemes belong to block-based framework. The framework simplifies the complexity of motion estimation, but gives over constraints to the motion field, which results in worse accuracy on the boundary of moving objects. This paper presents a novel technique for raising motion field accuracy. It uses several pre-defined pattern types to segment the motion fields of the previous frame of a sequence. The segmentation is based on the MAP framework that uses iterative method to obtain the solution. In addition, we develop a predictive scheme to predict the location of motion field discontinuities in the current frame, which further reduces the side information for the representation of segmentation.     

An FFT-based signal identification approach for obtaining the propagation constants of the leaky modes in layered media

We propose to find the propagation constants of modes in layered media by means of signal identification methods. To this effect we employ Cauchy's theorem, conformal mapping and Fast Fourier Transform (FFT) techniques to generate relevant Hankel moments, afterwards to be processed with selected signal identification algorithms. The method, terminated by a few Newton steps, provides a batch of highly accurate roots in appropriate disks or half-disks.     

Co(-Fe)-B-Si-Nb块体非晶合金

利用团簇线方法和微合金化原理研究了Co基Co(-Fe)-B-Si-Nb多组元合金体系中块体非晶合金的形成。首先,确定Co-B-Si三元体系为基础体系,利用团簇线(体现在三元体系中为二元特殊团簇与第三组元的连线)在Co-B-Si体系中确定基础合金成分;然后添加少量的Nb对基础三元成分进行合金化以提高合金的玻璃形成能力。利用铜模吸铸法制备直径为3mm的合金棒,结果表明能够形成块体非晶的合金成分为(Co8B3-Si)100-xNbx(x=4～5at%),其中,Co8B3为密堆附半八面体的阿基米德反棱柱团簇结构。并且这些非晶成分可近似地用(团簇)1(胶粘原子)1模型表达,为(Co8B3)1M1(M=(Si,Nb)),即非晶成分由一个团簇连接一个胶粘原子组成,其中胶粘原子M为Si和Nb原子的组合。最后用Fe替代部分Co可进一步提高合金的玻璃形成能力,得到的Co-Fe-B-Si-Nb五元块体非晶合金具有很好的软磁性能,其饱和磁化强度(Ms)最大可达0.98T,矫顽力(Hc)低于6A/m。     

Looking for narrow interfaces in automatic differentiation using graph drawing

Automatic differentiation is a powerful technique for evaluating derivatives of functions given in the form of a high-level programming language such as Fortran, C, or C++. This technique is superior, in terms of accuracy, to numerical differentiation because it avoids the truncation error involved in divided difference approximations. In automatic differentiation, the program is treated as a potentially very long composition of elementary functions to which the chain rule of differential calculus is applied over and over again. Because of the associativity of the chain rule, there is room for different strategies computing the same numerical results but whose computational cost may vary significantly. Several strategies exploiting high-level structure of the underlying computer code are known to reduce computational cost as opposed to blindly applying automatic differentiation. An example includes “interface contraction” where one takes advantage of the fact that the number of variables passed between subroutines is small compared with the number of propagated directional derivatives. Unfortunately, these so-called narrow interfaces are not immediately available. The present study investigates the use of the VCG graph drawing tool to recognize narrow interfaces in the computational graph, a certain directed acyclic graph used to represent data dependences of variables in the underlying computer code.     

Trust and conflict within virtual inter-organizational alliances: a framework for facilitating knowledge sharing

Trust and conflict are inherent issues of any organizational arrangement and central for knowledge sharing; yet they have received limited attention in the literature. In this paper, we undertake an investigation of both phenomena within the context of virtual alliances. A generic framework for understanding the dynamics of trust and conflict within the context of virtual inter-organizational arrangements is presented, followed by an examination of three distinct structural forms of virtual alliances, and strategies for generating trust and minimizing dysfunctional conflict. The paper concludes with an identification of avenues for further research.     

RE in schools: Learning the lessons of small scale renewables

Small-scale renewable energy schemes will play a vital role in achieving environmental targets, tackling climate change and mitigating against dwindling natural resources. However, finance is a big issue for many schools and homeowners so the continuation of grant funding will remain necessary to deliver these small-scale renewable energy projects. Grants also ‘prime the pump’ and stimulate future market growth, which ultimately will create the lower costs associated with a mass market.     

反思四级考试 提高教学质量

本文分析了大学英语四级考试与大学英语教学之间的关系,指出应正确对待四级考试,并提出一些提高大学英语教学质量,培养学生语言动用能力的措施。     

Using Information Retrieval techniques for supporting data mining

The classic two-stepped approach of the Apriori algorithm and its descendants, which consisted of finding all large itemsets and then using these itemsets to generate all association rules has worked well for certain categories of data. Nevertheless for many other data types this approach shows highly degraded performance and proves rather inefficient.

We argue that we need to search all the search space of candidate itemsets but rather let the database unveil its secrets as the customers use it. We propose a system that does not merely scan all possible combinations of the itemsets, but rather acts like a search engine specifically implemented for making recommendations to the customers using techniques borrowed from Information Retrieval.