ABSTRACT

In order to capture the effect of joint progressive stiffness degradation with the hardening effect taken into account, the three parametric continuous model is adopted hereafter for the analytical formulation. The current paper is an extension of the previous work (Gizejowski et al. 2012) giving all the details of the developed model together with a calibration procedure for basic model parameters. Experimental data used was obtained from laboratory tests carried out at the Warsaw University of Technology for beam-to-column joints of different reinforcement ratio. The results of calibration exercise as well as the values of calibrated model parameters are given for practical application.

This study focuses on methylol functional benzoxazines as precursors to build a network structure utilizing both benzoxazine and resole chemistry. The first part is a review of systems that contain methylol groups which play a role on their crosslinking formation. The polymerization mechanism and properties of resoles will be highlighted as the most abundant polymers that are characterized by polymerization through condensation reaction of methylol group. In the second part, the effect of incorporating methylol group into benzoxazine monomers is studied. Differential scanning calorimetry (DSC) is used to study the effect of methylol group on the rate of polymerization. Kissinger and Ozawa methods using non-isothermal DSC at different heating rates show that methylol monomer exhibits lower average activation energy compared to the un-functionalized monomer. The effect of adding catalysts into the monomers is …

The aim of this work was to establish the deformation behavior of two vanadium mic-roalloyed medium carbon steels with different contents of carbon and titanium by tensile testing at 77 K. Samples were reheated at 1250 C for 30 min and continuously cooled in still air. Beside acicular ferrite as the dominant morphology in both microstructures, the steel with lower content of carbon and negligible amount of titanium contains consi-derable fraction of grain boundary ferrite and pearlite. It was found that Ti-free steel exhibits a higher strain hardening rate and significantly lower elongation at 77 K than the fully acicular ferrite steel. The difference in tensile behavior at 77 K of the two steels has been associated with the influence of the pearlite, together with higher dislocation density of acicular ferrite.

The aim of this work was to determine TTT diagram of medium carbon V-N micro-alloyed steel with emphasis on the

development of intragranular ferrite morphologies. The isothermal treatment was carried out at 350, 400, 450, 500, 550

and 600 οC. These treatments were interrupted at different times in order to analyze the evolution of the microstructure.

Metallographic evaluation was done using optical and scanning electron microscopy (SEM). The results show that at high

temperatures (≥ 500 ○C) polygonal intragranulary nucleated ferrite idiomorphs, combined with grain boundary ferrite and

pearlite were produced and followed by an incomplete transformation phenomenon. At intermediate temperatures (450, 500

○C) an interloced acicular ferrite (AF) microstructure is produced, and at low temperatures (400, 350 ○C) the sheave of

parallel acicular ferrite plates, similar to bainitic sheaves but intragranularly nucleated were observed. In addition to sheaf

type acicular ferrite, the grain boundary nucleated bainitic sheaves are observed.

This paper presents empirical methods for enhancing the accuracy of inductive learning systems. It addresses the problems of: learning propositional production rules in multi-class classification tasks in noisy domains, maintaining continuous learning when confronted with new situation after the initial learning phase is completed, and classifying an object when no rule is satisfied for it.

It is shown that interleaving the learning and performance-evaluation process allows accurate classifications to be made on real-world data sets. The paper presents the system ARIS which implements this approach, and it is shown that the resulting classifications are often more accurate than those made by the non-refined knowledge bases.

The core design decision that lies behind ARIS is that it employs an ordering of the rules according to their weight. A rule’s weight is learned by using Bayes’ theorem to calculate weights for the rule’s conditions and combining them. This model focuses the analyses of the knowledge base and assists the refinement process significantly.

The system is non-interactive, it relies on heuristics to focus the refinement on those experiments that appear to be most consistent with the refinement data set. The design framework of ARIS consists of tabular model for expressing rule weights, and the relationship between refinement cases and the rules satisfied for each case to focus the refinement process. The system has been used to refine knowledge bases created by ARIS itself, as well as to refine knowledge bases created by the RIPPER and C4.5 systems in ten selected domains.

Problem statement: In the construction industry, success of building projects greatly depends on the client’s performance. The performance of clients is crucial since decisions made will influence the overall project performance. Typically, clients are represented by managerial and technical representatives during the design process. They play major roles in conveying required information to the design team regarding their future project. The quality of clients’ representatives has potential influence on design team performance. In designing green buildings client’s attributes are critical factors to high performance of building projects. Attributes such as knowledge and experience on green buildings, commitment level to green and clients’ ability to participate and manage design process are the key factors to produce green design. The propose of this study to identify current performance level of clients of building projects and establish key clients’ attributes influencing green design performance. Approach: To achieve mentioned aim a questionnaire survey was conducted to collect dada required. A sample of 274 respondents has been covered under the study, including architects and engineers practicing design and consultancy building sectors. Prior to analysis of data WINSTEPS software were used for Rasch modeling to determine validity and reliability of date. Descriptive analysis data includes quantitative and qualitative. Results and Conclusion: Client qualities in general were low, client communication with design team; client involvement and ability to coordinate design process were moderate. However, Knowledge and experience on green …

The polymerization mechanism of methylol-functional benzoxazine monomers is reported using a series of monofunctional benzoxazine monomers synthesized via a condensation reaction of ortho-, meta-, or para-methylol–phenol, aniline, and paraformaldehyde following the traditional route of benzoxazine synthesis. A phenol/aniline-type monofunctional benzoxazine monomer has been synthesized as a control. The structures of the synthesized monomers have been confirmed by ¹H NMR and FT-IR. The polymerization behavior of methylol monomers is studied by DSC and shows an exothermic peak associated with condensation reaction of methylol groups and ring-opening polymerization of benzoxazine at a lower temperature range than the control monomer. The presence of methylol group accelerates the ring-opening polymerization to give the ascending order of para-, meta-, and ortho-positions in …

Fuzzy decision forests aim to improve the predictive power of single fuzzy decision trees by allowing multiple views of the same domain to be modelled. Such forests have been successfully created for classification problems where the outcome field is discrete; however predicting a continuous output value is more challenging in combining the output from multiple fuzzy decision trees. This paper presents a new approach to creating fuzzy regression tree forests based upon the induction of multiple fuzzy regression decision trees from one training sample, where each tree will represent a different view of the data domain. The singular fuzzy regression trees are induced using a proven algorithm known as Elgasir which fuzzifies crisp CHAID decision trees using trapezoidal membership functions for fuzzification and applies Takagi-Sugeno inference to obtain the final predicted values. A modified version of Artificial Immune System Network model (opt-aiNet) is then used for the simultaneous optimization of the membership functions across all trees within the forest. A strength of the proposed method is that data does not require fuzzification before forest induction this reducing pre-processing time and the need for subjective human experts. Five problem sets from the UCI repository and KEEL repository are used to evaluate the approach. The experimental results have shown that fuzzy regression tree forests reduce the error rate compared with single fuzzy regression trees. 

In this paper we study the use of the Brill tagger [5,6,7] for tagging Modern Standard Arabic (henceforth MSA) text. The Brill tagger is a famous public domain part of speech tagger, originally designed for tagging English text by implementing machine learning approach through the method of transformation rules. IT had been adopted for other languages by many researchers [17,19,22]. Some modifications are needed on the learner and tagger that are written partly in perl and partly in C programming languages, and are run under the unix/linux operating system. The main change is done on the initial state tagger, which is used by both learner and tagger. A program is written using the lexical analyzer Lex to capture Arabic morphological structures, and then interfaced with both learner and tagger. The tagset used in this work is a revised version of that introduced by Khoja [11]. The revision included changing some of the tags for linguistic considerations and introducing some new tags to make the set more powerful, or to make up for limitations in the original tagset that hinder tagging some words. The corpus is obtained from two Jordanian magazines, and has to go through a series of editing steps. A collection of lexical rules and contextual rules are obtained and applied to Arabic text. The tagging accuracy of the resulting tagged text is measured now to be an average of up to about 84% for both known and unknown words, A rate, which is very promising for such a complex language and rich tagset. We still hope for better performance.

Abstract

The paper presents studies on numerical modelling of beam-to-column joint behaviour in typical service and exceptional design situations. The complexity of such investigations arises from highly nonlinear effects associated with the prediction of joint performance, such as structural imperfections, large displacements and rotations, inelastic properties of steel and concrete, bonding effects between steel and concrete, and slip between concrete and structural steel, among others. The paper addresses these problems and provides validation of numerical modelling techniques trough comparison with experimental data for joints under hogging and sagging moments. © (2012) Trans Tech Publications.