Locating complex eigenvalues for analytical eddy-current models used to detect flaws

2019 ◽  
Vol 38 (6) ◽  
pp. 1800-1809
Author(s):  
Grzegorz Tytko ◽  
Łukasz Dawidowski
Keyword(s):  
Eddy Current ◽  
Design Methodology ◽  
Complex Function ◽  
Precise Determination ◽  
Argument Principle ◽  
Content Type ◽  
Conductive Material ◽  
Complex Roots ◽  
Complex Eigenvalues

Purpose Discrete eigenvalues occur in eddy current problems in which the solution domain was truncated on its edge. In case of conductive material with a hole, the eigenvalues are complex numbers. Their computation consists of finding complex roots of a complex function that satisfies the electromagnetic interface conditions. The purpose of this paper is to present a method of computing complex eigenvalues that are roots of such a function. Design/methodology/approach The proposed approach involves precise determination of regions in which the roots are found and applying sets of initial points, as well as the Cauchy argument principle to calculate them. Findings The elaborated algorithm was implemented in Matlab and the obtained results were verified using Newton’s method and the fsolve procedure. Both in the case of magnetic and nonmagnetic materials, such a solution was the only one that did not skip any of the eigenvalues, obtaining the results in the shortest time. Originality/value The paper presents a new effective method of locating complex eigenvalues for analytical solutions of eddy current problems containing a conductive material with a hole.

Police crackdowns in Mexico City

2019 ◽  
Vol 42 (5) ◽  
pp. 798-813
Author(s):  
Ricardo Massa ◽  
Gustavo Fondevila
Keyword(s):  
Mexico City ◽  
Precise Determination ◽  
Crime Rates ◽  
Garch Models ◽  
Content Type ◽  
Sustained Reduction ◽  
Police Crackdown ◽  
The Impact ◽  
Static Nature

Purpose The purpose of this paper is to analyze the design and implementation of the police crackdown strategy employed in Mexico City and to discuss its limitations toward a medium-to-long-term reduction of crime rates for six types of robberies. Design/methodology/approach The present work employs generalized autoregressive conditional heteroscedasticity (GARCH) models to estimate the effect of police operations on the volatility of the rates of six types of robberies in Mexico City, as well as their persistence over time. Findings Results suggest that the concentration of policing in certain high-criminality spaces reduces crime rates in the immediate term; however, its permanence is contingent on policing design and behavioral characteristics of the targeted crime. Specifically, the Mexico City police crackdown strategy seems to be better suited for combating crimes of a “non-static” nature than those of a “static” nature. Research limitations/implications Due to the nature of the data used for this research, the performed analysis does not enable a precise determination of whether the crime rates respond to temporal or spatial displacement. Practical implications Considering the obtained results, a re-design of Mexico City’s police crackdown strategy is suggested for the sustained reduction of the number of reported cases of robberies of a static nature. Originality/value Despite their importance, few studies have measured the impact of police crackdowns on city-level crime rates and whether their effect is temporary or permanent. The present study proposes the use of GARCH models in order to integrate the study of this phenomenon into criminal time series models.

Causality in qualitative market and social research

2019 ◽  
Vol 22 (3) ◽  
pp. 405-413
Author(s):  
Clive Roland Boddy
Keyword(s):  
Qualitative Research ◽  
Design Methodology ◽  
Social Research ◽  
Pragmatic Approach ◽  
Social Phenomena ◽  
Content Type ◽  
The Past ◽  
The Moment ◽  
Practical Implications

Purpose Academic qualitative researchers have been criticized for rejecting the idea that their research can establish causality while market and social researchers, with their realist and pragmatic approach to research, take for granted that it can. This paper aims to explore the ability of qualitative research to determine cause and effect in terms of market and social phenomena. Design/methodology/approach The literature on causality in qualitative research is reviewed and discussed. The discussion is further informed by the author’s own experience of undertaking commercial and academic market and social qualitative research over the past 33 years. Findings In qualitative market and social research, the determination of causality is often needed but rarely discussed. This paper explores this occurrence and brings to the fore, via discussion and the use of example, the ways in which causality can be determined by qualitative research. Practical implications A determination of what events bring about predictable changes in social and market environments can be established via qualitative research particularly at a probabilistic level of causality. This implies that policymakers should give a greater emphasis to qualitative findings than then sometimes do at the moment. Originality/value Causality in market and social research is rarely discussed by practitioners but is nevertheless a premise of much of the qualitative research that is undertaken. This paper is therefore distinctive in that it examines whether this premise is justifiable.

Automated element grouping and self-stress identification of tensegrities

2015 ◽  
Vol 32 (6) ◽  
pp. 1643-1660 ◽  
Author(s):  
Kambiz Koohestani
Keyword(s):  
Design Methodology ◽  
Feasible Solution ◽  
State Of The Art ◽  
The Self ◽  
Content Type ◽  
Stress Mode ◽  
Novel Approach ◽  
Minimisation Problem ◽  
Feasible Solutions

Purpose – The determination of feasible self-stress modes and grouping of elements for tensegrities with predefined geometry and multiple self-stress modes is very important, though difficult, in the design of these structures. The purpose of this paper is to present a novel approach to the automated element grouping and self-stress identification of tensegrities. Design/methodology/approach – A set of feasible solutions conforming to the unilateral behaviour of elements is obtained through an optimisation process, which is solved using a genetic algorithm. Each chromosome in the population having a negative fitness is a distinctive feasible solution with its own grouping characteristic, which is automatically determined throughout the evolution process. Findings – The self-stress identification is formulated through an unconstrained minimisation problem. The objective function of this minimisation problem is defined in such a way that takes into account both the feasibility of a solution and grouping of elements. The method generates a set of feasible self-stress modes rather than a single one and automatically and simultaneously suggests a grouping of elements for every feasible self-stress mode. A self-stress mode with a minimal/subminimal grouping of elements is also obtained. Originality/value – The method can efficiently generate sets of feasible solutions rather than a single one. The authors also address one of the challenging issues related to this identification, i.e., automated grouping of elements. These features makes the method very efficient since most of the state-of-the-art methods address the self-stress identification of tensegrities based on predefined groupings of elements whilst providing only a single corresponding solution.

An efficient reformulation of a multiscale method for the eddy current problem

2017 ◽  
Vol 36 (5) ◽  
pp. 1421-1429
Author(s):  
Markus Schöbinger ◽  
Karl Hollaus ◽  
Joachim Schöberl
Keyword(s):  
Eddy Current ◽  
Design Methodology ◽  
Degrees Of Freedom ◽  
Current Problem ◽  
Multiscale Method ◽  
Content Type ◽  
Eddy Current Problem ◽  
Laminate Thickness ◽  
The Cost ◽  
Laminated Material

Purpose This paper aims to improve the efficiency of a numerical method to treat the eddy current problem on a laminated material, where using a mesh that resolves each individual laminate would be too computationally expensive. Design/methodology/approach The domain is modeled using a coarse mesh that treats the laminated material as a bulk with averaged properties. The fine-structured behavior is recovered by introducing micro-shape functions in the ansatz space. One such method is analyzed to find further model restrictions. Findings By using a special reformulation, it is possible to eliminate the additional degrees of freedom introduced by the multiscale ansatz at the cost of an additional modeling error that decreases with the laminate thickness. Originality/value The paper gives a computationally more efficient approximate variant to a known multiscale method.

Profit-sharing investment accounts in islamic banks or mutualization, accounting perspective

2016 ◽  
Vol 14 (1) ◽  
pp. 30-48 ◽  
Author(s):  
Wasim K. AlShattarat ◽  
Muhannad A. Atmeh
Keyword(s):  
Financial Reporting ◽  
Mutual Fund ◽  
Design Methodology ◽  
Profit Sharing ◽  
Islamic Banks ◽  
Content Type ◽  
Implementation Challenges ◽  
Total Profit ◽  
Practical Implications

Purpose Islamic banks use Mudarabah contract to replace the interest-bearing deposits with profit-sharing investment accounts. The purpose of this paper is to explore the challenges and problems associated with the employment of Mudarabah contract by Islamic banks. Design/methodology/approach The study critically analyzes the Mudarabah contract used by Islamic banks. It reviews the evolution of the contract from its traditional type to more complicated types such as compound, unrestricted, commingled and continuous Mudarabah. The paper investigates the problems that have emerged from implementing such types in current business settings. Findings The paper proves that implementing the Mudarabah contract by banks imposes several problems among which are the following: difficulty in the determination of total profit resulting from Mudarabah and in allocating this profit to the multiple parties involved in Mudarabah; usage of reserves to cater against future losses may undermine the concept of Mudarabah profit-loss sharing and lead to earnings management; corporate governance is also a major problem in Mudarabah contract, as the depositors are exposed to risks but have no governance rights; and Mudarabah may also lessen the fair presentation of financial reporting. Research limitations/implications The paper examines the evolving Mudarabah contract and its implementation challenges, based on available literature (no empirical analysis was conducted). Practical implications The implications are significant for the future development of Islamic contracts and Islamic accounting treatments. Originality/value Many studies explored the Mudarabah contract from a Shariah or law perspective. However, this paper investigates the Mudarabah contract with a focus on the implication on accounting and financial reporting because of the lack of studies in this area. Furthermore, it demonstrates the persistent flaws in the Mudarabah contract, and it proposes a new model for mobilizing funds, i.e. mutual fund.

Evaluation of residual clearance after pre-joining and pre-joining scheme optimization in aircraft panel assembly

2016 ◽  
Vol 36 (4) ◽  
pp. 376-387 ◽  
Author(s):  
Di Yang ◽  
Weiwei Qu ◽  
Yinglin Ke
Keyword(s):  
Pareto Optimality ◽  
Design Methodology ◽  
Elastic Behavior ◽  
Assembly Model ◽  
Content Type ◽  
Scheme Optimization ◽  
Constrained Variation ◽  
Practical Implications ◽  
Excessive Number

Purpose For the automatic drilling and riveting in panel assembly, gaps between the skin and strangers are inevitable and undesirable. At present, the determination of pre-joining schemes relies on workers’ experience, introducing excessive number and inappropriate locations of pre-joining. This paper aims to present a new method for the evaluation of residual clearances after pre-joining and the pre-joining scheme optimization, providing operation guidance for the workers in panel assembly workshop. Design/methodology/approach In this paper, an equivalent gap assembly model for pre-joining is proposed on the basis of the mechanism of variation. This model retains the essential elastic behavior of the key features during the pre-joining operation and calculates the residual clearances in the view of the potential energy. Subsequently, this method is embedded into a Pareto optimality-based genetic algorithm, and the optimal pre-joining schemes are achieved with the consideration of the total residual clearances and the permissive tolerances. Findings The equivalent gap assembly model has the capability to predict an acceptable degree of accuracy of the residual clearances and achieve the optimized pre-joining schemes with less number of pre-joining at the same level of residual clearances. Practical implications The optimized pre-joining schemes are given in the form of Pareto optimality set, and workers can select suitable results according to their inclination to the quality and efficiency. Originality/value The paper is the first to propose the equivalent gap assembly model for the pre-joining operation, which provides for the simplification of the calculation of residual clearances based on the constrained variation principles.

Evaluation of corrosion inhibitors in acid medium

2015 ◽  
Vol 62 (4) ◽  
pp. 241-245
Author(s):  
Fernando Benedicto Mainier ◽  
Raphaela de Melo Baêsso e Silva
Keyword(s):  
Carbon Steel ◽  
Corrosion Inhibitor ◽  
Acid Medium ◽  
Design Methodology ◽  
Corrosion Inhibitors ◽  
Experimental Conditions ◽  
Content Type ◽  
Steel Pipes ◽  
Kinetics Of

Purpose – The purpose of this paper is to evaluate the corrosion inhibitor performance in acid medium through the determination of Fe2+ ions present based on reaction kinetics of steel with the acid. The use of corrosion inhibitors has been an excellent technique for protecting carbon steel pipes acidizing operations in oil wells. The inhibitor forms a chemical barrier on the metal surface that prevents or reduces attack by the acidic media. Design/methodology/approach – The experimental study provides a methodology to evaluate the performance of corrosion inhibitors in an acid medium, preferentially of concentrated hydrochloric acid. The process consists essentially of total immersion coupons of carbon steel, with continuous stirring, controlled temperature and quantitative determinations of iron ions from the dissolution of steel. The additions of commercial corrosion inhibitor base of ethoxylated amines of high molecular weight in an acid medium showed excellent performance at a temperature ranging from 25 to 45°C. Findings – This paper presents the mechanisms of protection, performance graphs and calculations of the activation energies of the addition of corrosion inhibitors in an acidic medium. Originality/value – The originality of this essay is to evaluate and correlate the performance of corrosion inhibitors with the activation energy in experimental conditions.

The phonological process of Rongga language from the phonemic into phonetic realization

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
I Nyoman Suparsa
Keyword(s):  
Data Analysis ◽  
Design Methodology ◽  
Additional Data ◽  
Primary Data ◽  
Phonological Process ◽  
Content Type ◽  
Monosyllabic Words ◽  
Written Materials ◽  
Phonetic Realization

PurposeThe current study aims firstly to explain the origin of the morphemic segments of Rongga language, either at the phonological or the phonetic level and the terms of the morphemic structure of Rongga, whether related to positive or if-then conditions. The second objective is to describe the phonological process of Rongga from the changing process of phonemic into phonetic realization.Design/methodology/approachAs far as the methodology is concerned, three methods are applied including (1) method of collecting data, (2) data analysis methods and (3) method of presenting the result of data analysis. The literary method is defined as a way of obtaining written materials that can support the primary data as additional data.FindingsThe findings of compression placement on Rongga reveal that firstly, the monosyllabic words, whether or not preceded by a consonant, whether or not preceded by a consonant stressed on a single syllable and whether or not preceded by a consonant or before the second syllable, both of which either precedes the consonant or do not follow a word boundary. Second, three and four monosyllabic words will be stressed on the last syllable if they precede the consonant or not.Originality/valueThe results are expected to be considered as one of the primary contributions to the determination of the orthographic system of Rongga, in particular, the consonant and unique vowel in Rongga.

Buckling capacity of cold-formed steel structure column member with perforation section in affordable house framing system

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fatimah De'nan ◽  
Nor Salwani Hashim ◽  
Zafira Nur Ezzati Mustafa
Keyword(s):  
Design Methodology ◽  
Steel Structure ◽  
Construction Sector ◽  
Content Type ◽  
Circular Shape ◽  
Edge Distance ◽  
Cold Formed Steel ◽  
Wall Construction ◽  
Affordable House

Purpose The purpose of this study is to know the buckling capacity for cold-formed C-column with perforation. Cold-formed C-column have been used in interior wall construction. The concept of web perforation in the column has been introduced to the construction sector to overcome the issue of material cost. Design/methodology/approach Initially, the determination of the suitable spacing for the space column for the affordable house is investigated. Analysis house frame has been done in STAAD Pro. (Staad Pro, 2003) software using cold-formed C-column without perforation. Perforation with circular shape has been used in this study with the size of 0.4, 0.6 and 0.8 D (D = 180 mm). Perforation spacing is 150, 250 and 350 mm are adopted. Findings For the specimen with 0.4 D perforation and the edge distance is 539 mm have the highest buckling capacity (26.59 kN). Reduction of buckling capacity is 5.31% from cold-formed C-column without perforation and reduction of the volume is −2.16%. For the same case with 0.8 D perforation, the buckling capacity reduces with 22.52% and volume is −6.85%. Originality/value The conclusion of this analysis, C-column without perforation have higher buckling capacity compare to C-column with perforations.

Optimization of the heat flow by solving inverse problem in the protective layer of the TPS panel

2019 ◽  
Vol 30 (6) ◽  
pp. 2989-3003 ◽  
Author(s):  
Łukasz Brodzik ◽  
Andrzej Frąckowiak
Keyword(s):  
Protective Layer ◽  
Inverse Heat Conduction ◽  
Insulation Layer ◽  
Protective Properties ◽  
Content Type ◽  
Conductive Material ◽  
Time Extension ◽  
Inverse Heat Conduction Problems ◽  
Heating Up

Purpose This paper aims to present the problem of heating the damaged insulation of an orbiter. Design/methodology/approach Changes of the insulation’s thermal properties, made by adding conductive material of high value of specific heat in a form of a dope to the protective layer, were examined. An iterative algorithm determining a variable of dope concentration in the material was developed. Findings Determination of distribution of conductive material concentration was made for materials which, after verification, demonstrated the most beneficial effect on protective properties of the modified insulation layer. The problem of determining the distribution of metal filings concentration in the insulation layer of the coating belongs to inverse heat conduction problems. Originality/value Change of properties was to enable time extension of the LI900 insulation tile heating up to the maximal temperature and, additionally, to lowering this temperature.

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