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Article
Publication date: 27 November 2018

Hassan Rezayat, Jared Richard Bell, Alex J. Plotkowski and Sudarsanam S. Babu

The purpose of this paper is to introduce the multi-solution nature of topology optimization (TO) as a design tool for additive manufacturing (AM). The sensitivity of…

Abstract

Purpose

The purpose of this paper is to introduce the multi-solution nature of topology optimization (TO) as a design tool for additive manufacturing (AM). The sensitivity of topologically optimized parts and manufacturing constraints to the initial starting point of the optimization process leading to structures with equivalent performance is explored.

Design/methodology/approach

A modified bi-directional evolutionary structural optimization (BESO) code was used as the numerical approach to optimize a cantilever beam problem and reduce the mass by 50 per cent. Several optimized structures with relatively equivalent mechanical performance were generated by changing the initial starting point of the TO algorithm. These optimized structures were manufactured using fused deposition modeling (FDM). The equivalence of strain distribution in FDM parts was tested with the digital image correlation (DIC) technique and compared with that from the modified BESO code.

Findings

The results confirm that TO could lead to a wide variety of non-unique solutions based on loading and manufacturability constraints. The modified BESO code was able to reduce the support structure needed to build the simple two-dimensional cantilever beam by 15 per cent while keeping the mechanical performance at the same level.

Originality/value

The originality of this paper lies in introduction and application of the multi-solution nature of TO for AM as a design tool for optimizing structures with minimized features in the overhang condition and the need for support structures.

Details

Rapid Prototyping Journal, vol. 25 no. 9
Type: Research Article
ISSN: 1355-2546

Keywords

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Book part
Publication date: 14 December 2018

Ramazan Yildirim and Mansur Masih

The purpose of this chapter is to analyze the possible portfolio diversification opportunities between Asian Islamic market and other regions’ Islamic markets; namely USA…

Abstract

The purpose of this chapter is to analyze the possible portfolio diversification opportunities between Asian Islamic market and other regions’ Islamic markets; namely USA, Europe, and BRIC. This study makes the initial attempt to fill in the gaps of previous studies by focusing on the proxies of global Islamic markets to identify the correlations among those selected markets by employing the recent econometric methodologies such as multivariate generalized autoregressive conditional heteroscedastic–dynamic conditional correlations (MGARCH–DCC), maximum overlap discrete wavelet transform (MODWT), and the continuous wavelet transform (CWT). By utilizing the MGARCH-DCC, this chapter tries to identify the strength of the time-varying correlation among the markets. However, to see the time-scale-dependent nature of these mentioned correlations, the authors utilized CWT. For robustness, the authors have applied MODWT methodology as well. The findings tend to indicate that the Asian investors have better portfolio diversification opportunities with the US markets, followed by the European markets. BRIC markets do not offer any portfolio diversification benefits, which may be explained partly by the fact that the Asian markets cover partially the same countries of BRIC markets, namely India and China. Considering the time horizon dimension, the results narrow down the portfolio diversification opportunities only to the short-term investment horizons. The very short-run investors (up to eight days only) can benefit through portfolio diversification, especially in the US and European markets. The above-mentioned results have policy implications for the Asian Islamic investors (e.g., Portfolio Management and Strategic Investment Management).

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Article
Publication date: 28 January 2020

Fahad Almudhaf and Bader Alhashel

This paper aims to investigate the pricing efficiency of Saudi Sharia-compliant (i.e. Islamic) exchange-traded funds (ETFs).

Abstract

Purpose

This paper aims to investigate the pricing efficiency of Saudi Sharia-compliant (i.e. Islamic) exchange-traded funds (ETFs).

Design/methodology/approach

The paper adheres to a positivist research philosophy with a deductive research approach where data is collected, analyzed and interpreted to examine a hypothesis. Ordinary least squares (OLS) regressions are applied to investigate pricing efficiency and persistence.

Findings

The results show that Saudi ETFs do not currently offer proper diversification for investors, possibly due to their low trading volumes and the delays of market prices in reflecting net asset value (NAV). On average, ETFs trade at a premium to their NAVs. Moreover, the authors find that the deviations of ETF prices from their NAVs (i.e. premiums or discounts) do not disappear in one day. The results reveal a significant positive relationship between the trading volume of Saudi ETFs and volatility, a significant positive correlation between ETF returns and contemporaneous deviations and a significant negative relationship between returns and lagged deviations. These findings can be interpreted as evidence against the market efficiency of Saudi ETFs.

Practical implications

Individual and institutional investors can use Saudi ETFs, especially as their efficiency improves with increased trading volume (liquidity). Saudi regulators must increase their efforts to educate market participants and expand the availability of information to enhance transparency and awareness of the benefits of investing in ETFs, which will positively affect liquidity and pricing efficiency in the future.

Originality/value

This paper is the first to perform empirical tests on Saudi ETFs. Saudi Arabia deserves further attention because it is the most significant stock market in the Gulf Cooperation Council and only recently allowed foreigners to participate.

Details

Journal of Islamic Accounting and Business Research, vol. 11 no. 4
Type: Research Article
ISSN: 1759-0817

Keywords

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Article
Publication date: 1 December 2001

Jaroslav Mackerle

Gives a bibliographical review of the finite element meshing and remeshing from the theoretical as well as practical points of view. Topics such as adaptive techniques for…

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Abstract

Gives a bibliographical review of the finite element meshing and remeshing from the theoretical as well as practical points of view. Topics such as adaptive techniques for meshing and remeshing, parallel processing in the finite element modelling, etc. are also included. The bibliography at the end of this paper contains 1,727 references to papers, conference proceedings and theses/dissertations dealing with presented subjects that were published between 1990 and 2001.

Details

Engineering Computations, vol. 18 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

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